feat(npm): restore programmatic/embedded SDK API (#354) (#603)

The 0.9.x thin-installer turned @colbymchenry/codegraph into a bin-only
shim: require("@colbymchenry/codegraph") threw MODULE_NOT_FOUND and no
types shipped, breaking embedded library consumers (e.g. Electron apps)
upgrading from 0.8.0.

Restore programmatic use without re-bloating the thin shim or duplicating
the ~49 MB of grammars the per-platform bundle already carries:

- main -> npm-sdk.js re-exports the installed per-platform bundle's compiled
  library (lib/dist/index.js) at runtime, reusing that bundle's own deps; it
  falls back to a self-healed cache bundle, else throws an actionable error.
- types -> ship the .d.ts tree only (~590 KB) in the main package, built from
  the same release so it can never skew from the runtime it re-exports.
- exports map resolves the `types` condition (nodenext) and the default entry.
- DatabaseConnection + QueryBuilder are now top-level exports, so embedded
  callers get the building blocks from the package entry instead of deep
  dist/ imports (which the shim no longer ships).

The CLI/MCP `bin` keeps execing the bundled Node; only library consumers run
on their own runtime, which must be Node 22.5+ for the built-in node:sqlite.

Validated end-to-end: built a real darwin-arm64 bundle, packed the npm
packages, installed them into a throwaway consumer, and confirmed require()
plus a full init/indexAll/searchNodes round-trip and the low-level
DatabaseConnection/QueryBuilder path all work on the host Node; types resolve
under both nodenext and classic node resolution; and the CLI shim still
launches. New hermetic tests cover npm-sdk resolution, cache fallback, and the
missing-bundle error.

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

CHANGELOG.md

@@ -17,6 +17,7 @@ and adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 - 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.
+- CodeGraph is usable as an embedded library again: `require("@colbymchenry/codegraph")` and `import` now resolve the programmatic API — the `CodeGraph` class plus building blocks like `DatabaseConnection`, `QueryBuilder`, `initGrammars`, and `FileLock` — so you can drive the graph directly from your own app (for example an Electron process) instead of only through the CLI or MCP server. Embedding runs on your own runtime, so it needs Node 22.5+ for the built-in SQLite. (#354)
 
 ### Fixes