fix(vscode): adopt a same-key pending lint runtime instead of restarting it

[fi3ework]

Summary

Fixes a startup teardown race reported from a real user log: at activation, the first lint worker was SIGTERMed ~1.1s after spawn — while the LSP initialize was still in flight — then an identical runtime (same core, same shim, same runtime key) started successfully right after. vscode-languageclient force-notifies "Server initialization failed" / "couldn't create connection to server" when its in-flight initialize is severed (verified against vscode-languageclient 9.0.1; those toasts cannot be suppressed via client options), so users saw scary error popups for what was a self-healing restart.

Root cause: RuntimeManager.reconcile() swept the document's pending runtime uses before resolving what the new pass would land on. The register-time reconcile, a detection pass and didOpen routinely land inside one worker startup window, so the second reconcile dropped the not-yet-bound entry's refcount to zero and tore the runtime down mid-initialize, even though it then resolved to the very same key.

Fix (both ahead-of-upstream, recorded in AGENTS.md to offer back on the next sync):

• RuntimeManager.reconcile now resolves the document's core first (planDocumentCore); the pending-use sweep keeps a pending entry whose key matches the plan, adopting the in-flight start instead of restarting it. A key change still cancels the pending start immediately (a hung start cannot block the per-document tail), and a superseded operation leaves the entry's fate to the newest reconcile's sweep.
• Rslint.close() gives a still-Starting client one bounded chance (2s, shared CLOSE_SETTLEMENT_TIMEOUT_MS) to settle before tearing down the transport, covering the legitimate mid-start closes (document closed during start, core key changed). The pre-teardown wait subsumes the old post-dispose start wait, so a hung start pays the bound once. Planned aborts (close/supersede) are no longer logged as errors.

Verification: new regression suite tests/stacks/lint/runtimeManager.test.ts (same-key adoption — red before the fix; changed-key immediate cancel; document-close release), pnpm lint (type-checked) clean, full unit suite green, lint E2E slice (13 suites) all passing.

Related Links

• Upstream RuntimeManager (web-infra-dev/rslint packages/vscode-extension) carries the same sweep ordering; both fixes are candidates to send upstream on the next sync.

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).