feat(mcp): trace relevance + closure-collection + god-file rendering + cold-start handshake (#580)

Trace endpoint relevance (overloaded names resolve to the real implementation instead of an empty protocol/delegate stub), Swift closure-collection synthesizer, multi-phase god-file explore rendering, and serve --mcp cold-start handshake sped ~811ms→~90ms (proxy answers initialize/tools-list locally). Full suite green (1090 pass).

CHANGELOG.md

@@ -14,9 +14,14 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 - `codegraph init` now builds the initial index by default — you no longer need the `-i`/`--index` flag (it's still accepted, so existing commands and scripts keep working). (#483)
 - Go: Gin middleware chains now connect end-to-end in `codegraph_trace` and `codegraph_explore` — following a request reaches the middleware and route handlers registered via `.Use()` / `.GET()` instead of dead-ending where the framework dispatches the chain dynamically.
 - `codegraph_explore` now sizes its response to the *answer* instead of the file count: it shows the mechanism and the exact methods you asked about in full — even when they're buried deep in a large file — while collapsing the redundant interchangeable implementations of an interface (an HTTP interceptor chain, a query-compiler family) down to signatures. Fewer tokens for a more complete answer, so on the flows that used to occasionally cost more than plain grep/read it's now clearly cheaper — and the win holds across small, medium, and large codebases. Distinct, non-interchangeable code is shown in full as before. Disable with `CODEGRAPH_ADAPTIVE_EXPLORE=0`.
+- Swift deferred-validation flows (and similar "handler array" patterns) now connect end-to-end in `codegraph_trace` and `codegraph_explore` — following a request's lifecycle reaches the validators registered with `.validate { … }` instead of dead-ending where the framework runs them by iterating a stored list of closures. Any pattern where closures are appended to a collection and later invoked by looping over it is now traced.
+- `codegraph_explore` now spells out the dynamic-dispatch relationships of the symbols you ask about — e.g. "the closures registered here are run by `didCompleteTask`" — so the indirect hops you'd otherwise grep to reconstruct are listed alongside the call flow.
+- `codegraph_explore` answers multi-phase questions that span a large "god file" far more completely. For a flow like "build, send, and validate a request" — where one big file holds the build chain and the validate logic lives in others — it now keeps every method *on the flow path* in full, collapses the file's off-path methods to one-line signatures, and guarantees each phase's defining file is shown (instead of truncating at a fixed size and dropping whichever phase came last, which sent you to read it by hand). Incidental files that merely name-drop the flow are still trimmed, so the response stays focused on the code that answers the question.
 
 ### Fixes
 
+- `codegraph_trace` now resolves an overloaded symbol name to its real implementation instead of an empty protocol/delegate stub. Tracing a flow through a heavily-overloaded API (common in Swift, Java, C#, and Go) could land on an unrelated no-op method that happened to share the name and report "no path"; it now picks the substantive definition the flow actually runs through.
+- CodeGraph's MCP server now answers an agent's opening handshake the instant it launches instead of blocking while the index loads, so a fresh session's very first tool call no longer occasionally races a server that's still warming up and falls back to grep/read. The first question in a new session now reliably goes through CodeGraph.
 - Indexing a project that contains only config-style files (YAML, Twig, or `.properties`) no longer misleadingly reports "No files found to index" — these files are tracked at the file level and are now counted as indexed. Thanks @luojiyin1987 (#357).
 
 ## [0.9.7] - 2026-05-28