feat(resolution): bridge MediatR Send/Publish to its IRequestHandler.Handle

MediatR decouples a _mediator.Send(x)/.Publish(x) call from the Handle method
that runs it, linked by the request/notification TYPE (the IRequestHandler<X,…>
generic), usually across files in a Clean Architecture layout — so flows
dead-end at the mediator call and the agent reads to find the handler.
mediatrDispatchEdges bridges each dispatch -> the matching handler's Handle.

Same two-pass, type-keyed shape as the Spring synthesizer, with two C#-specific
twists found by probing:

- C# method nodes carry NO signature (csharp.ts defines no getSignature), so
  Pass 1 reads the request type from the handler CLASS base-list source
  (`: IRequestHandler<X,…>` first generic arg) and binds the class's Handle.
- The dominant .NET idiom is VARIABLE-passed, not inline `Send(new X)` — eShop
  has zero genuine inline MediatR sends. So Pass 2 resolves the sent type from
  the argument three ways within the enclosing method: inline `new X(…)`, a
  local `var v = new X(…)` (backward scan), or a parameter/local declared `X v`.

Two precision gates: the receiver must be mediator-ish (mediator/sender/
publisher — excludes MAUI MessagingCenter.Send, HttpClient.Send) AND the
resolved type must have a handler (so a same-named non-request DTO is never
bridged). Handles the IdentifiedCommand<T,R> wrapper and void IRequestHandler<T>.

Surfaces as `dynamic: mediatr dispatch` via the generic synth-edge fallback.

Validated 100% precision on two grep-confirmed repos: jasontaylordev/
CleanArchitecture (small, 9 edges, inline + param forms) and dotnet/eShop
(medium, 9 edges, 0 false positives, variable-passed + IdentifiedCommand +
the CancelOrderCommand DTO-collision correctly avoided); 0 on the
Newtonsoft.Json control. Node-stable (pure edge synth). Suite 1619 green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/design/dispatch-synthesizer-backlog.md

@@ -63,7 +63,7 @@ Status legend (matches the playbook): ✅ done+validated · 🟡 shipped but und
 
 | Shape | Ecosystem | Anchor | Mechanism | Status |
 |---|---|---|---|---|
-| **MediatR / CQRS** | .NET | `IRequest<T>` → `IRequestHandler<TReq,T>` by the generic request type; `_mediator.Send(new GetFooQuery())` → handler | S (generic-type-keyed) | 🔬 named a frontier in CLAUDE.md, but it's statically keyable via the generic — worth a real attempt |
+| **MediatR / CQRS** | .NET | `_mediator.Send(x)`/`.Publish(x)` → the `Handle` of `IRequestHandler<X,…>`/`INotificationHandler<X>` by request type | S (type-keyed, 2-pass + arg resolution) | ✅ **SHIPPED (2026-06-20)** — `synthesizedBy:'mediatr-dispatch'` (`mediatrDispatchEdges`). Same 2-pass type-keyed shape as Spring, with a twist: **C# method nodes have NO `signature`** (csharp.ts defines no `getSignature`), so Pass 1 reads the request type from the handler **class base-list source** (`: IRequestHandler<X,…>` — first generic arg), not a param signature, and binds the class's `Handle` method. **The dominant .NET idiom is VARIABLE-passed, not inline** — eShop had **0** genuine inline `Send(new X)` (every send is `mediator.Send(command)`), so Pass 2 RESOLVES the sent type from the argument three ways within the enclosing method: inline `new X(…)`, a local `var v = new X(…)` (backward scan, wins), or a parameter/local declared `X v`. **Two precision gates:** (1) receiver must be mediator-ish (`/mediator|sender|publisher/i` — excludes MAUI `MessagingCenter.Send`, `HttpClient.Send`), (2) resolved type must be in the handler map (so eShop's same-named `CancelOrderCommand` DTO in ClientApp, which has no handler, is never bridged). Handles the `IdentifiedCommand<T,R>` wrapper (sent + handled at that layer) and void single-arg `IRequestHandler<T>`. **100% precision: jasontaylordev/CleanArchitecture (small, 9 edges, inline + param forms) + dotnet/eShop (medium, 9 edges, 0 FP, variable-passed + IdentifiedCommand + DTO-collision avoided); 0 on the Newtonsoft.Json control.** Node-stable (pure edge synth). Surfaces `dynamic: mediatr dispatch`. `+ mediatr-dispatch-synthesizer.test.ts`. **Deferred (recall):** generic `_mediator.Publish(domainEvent)` over a collection (concrete type erased at the publish site — eShop's DDD AddDomainEvent fan-out), `record`-positional or factory-built args whose type isn't a `new X`/param, the `ICommandHandler<T>` facade indirection (modular-monolith). |
 | **Celery** | Python | `@shared_task`/`@app.task`/`@<app>.task`/`@task` def + `.delay()`/`.apply_async()` call → task body | S (decorator-gated name) | ✅ **SHIPPED (2026-06-20)** — `synthesizedBy:'celery-dispatch'` (`celeryDispatchEdges`). Link the enclosing fn at each `.delay(`/`.apply_async(` site → the task fn. Precision rests on the DECORATOR gate: the dispatched name must resolve to a Python `function` carrying a task decorator, read from the source lines ABOVE its `def` (the def's own startLine excludes the decorator; no `decorates` edge exists — `@shared_task` is an unresolved external import). `kind==='function'` filter drops the same-named test-method collision (`consume_file`). Canvas forms (`group(t).delay()`, `t.s()`/`.si()`) have no single identifier before `.delay` → skipped, not mis-bridged. Cross-module name collision → same-file preference else bail. **100% precision: paperless-ngx (small, `@shared_task`, 31 edges, 31/31 real), pretix (medium, `@app.task`, 63 edges across 21 tasks, 0/21 FP); 0 on the httpie control (no Celery).** Node-stable (pure edge synth, no extraction change). Surfaces as `dynamic: celery dispatch @site` via the generic fallback. `+ celery-dispatch-synthesizer.test.ts`. **Deferred (recall):** canvas dispatch, class-based `Task` subclasses, `app.send_task('dotted.name')` string dispatch, aliased imports (`import send_email as s; s.delay()`). |
 | **Sidekiq** | Ruby | `class W; include Sidekiq::Job; def perform; end` + `W.perform_async(...)` → `perform` | S (class→perform) | ⬜ — the Ruby sibling of Celery; build next-to-it (grep-confirm ≥2 `perform_async` repos). |
 | **Spring events** | Java | `publishEvent(new XEvent(…))` → `@EventListener`/`@TransactionalEventListener`/`ApplicationListener<X>` by event type | S (type-keyed, 2-pass) | ✅ **SHIPPED (2026-06-20)** — `synthesizedBy:'spring-event'` (`springEventEdges`). Pass 1 builds `Map<eventType, listenerMethod[]>` — listeners are `@EventListener`/`@TransactionalEventListener` methods (event type = the first param type off the node `signature`, or the `@EventListener(X.class)` value form) + `class … implements ApplicationListener<X>` `onApplicationEvent` methods (name + file `ApplicationListener<` gate). Pass 2 links each `publishEvent(new XEvent(…))` site's enclosing method → every listener of XEvent. **KEY Java fact:** a method node's range INCLUDES its leading annotations (`startLine` = first `@…` line, NOT the `public void` decl), so the annotation gate scans DOWNWARD from startLine, bounded to consecutive `@`-lines (no bleed into an adjacent method). Keyed by EXACT type name, no name resolution — precision is structural (param type ↔ `new X` type). Multi-line `publishEvent(\n new X(…))` handled (`\s*` spans newlines). **100% precision: halo (medium, 1254 java, 33 edges across 24 events, 0 publisher/listener FP, all 3 listener forms + fan-out) + thombergs/code-examples (4 edges incl. the `@TransactionalEventListener` form halo lacks); 0 on the gson control (no Spring).** Node-stable (pure edge synth). Surfaces `dynamic: spring event @site`. `+ spring-event-synthesizer.test.ts`. **Deferred (recall):** `publishEvent(bareVar)` (needs the var's declared type), Spring's listener-return-value re-publish, `@DomainEvents`/`AbstractAggregateRoot.registerEvent`, generic `PayloadApplicationEvent<X>` params. |
@@ -88,6 +88,7 @@ Status legend (matches the playbook): ✅ done+validated · 🟡 shipped but und
 | Vuex dispatch | `vuex-dispatch` | ✅ **shipped (2026-06-20)** — string `dispatch('ns/action')`/`commit('M')` → handler; 100% precision element-admin (55) / vue-admin-template (12) / d2-admin (63), 0 on Redux controls. |
 | Celery | `celery-dispatch` | ✅ **shipped (2026-06-20)** — `.delay()`/`.apply_async()` → `@shared_task`/`@app.task` body; 100% precision paperless-ngx (31) / pretix (63 across 21 tasks), 0 on httpie control. Decorator-gated via source above the `def`. |
 | Spring events | `spring-event` | ✅ **shipped (2026-06-20)** — `publishEvent(new XEvent)` → `@EventListener`/`@TransactionalEventListener`/`ApplicationListener<X>` by event type; 100% precision halo (33 across 24 events) / code-examples (4), 0 on gson control. Type-keyed 2-pass, no name resolution. |
+| MediatR | `mediatr-dispatch` | ✅ **shipped (2026-06-20)** — `_mediator.Send(x)`/`.Publish(x)` → the `Handle` of `IRequestHandler<X>`/`INotificationHandler<X>` by request type; 100% precision jasontaylor (9) / eShop (9, variable-passed), 0 on Newtonsoft control. Type from class base-list (C# has no signature) + arg resolved inline/local/param; receiver + handler-map gates. |
 | (see playbook §6 / `callback-synthesizer.ts` for the other ~20 channels) | | |
 
 ### redux-thunk follow-ups (found by the n>1 validation — this is exactly what it's for)