PR #183: Restrict sessionKey regex to [a-zA-Z0-9_-]+ and add
startsWith containment check to prevent path traversal in
writeRoutingInstructions workspace derivation.

PR #190: Fix getRuntimeSummary() bun detection — use endsWith("bun")
instead of === "bun" to handle full paths like ~/.bun/bin/bun.

PR #192: Remove trailing whitespace from AGENTS.md blank separator lines.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

#731)

ctx_execute(language: "javascript") failed when context-mode runs
in-process inside a bun-compiled self-contained binary host
(OpenCode opencode.exe / Kilo). PolyglotExecutor spawned the host
binary itself with a script.js argument, triggering yargs's
"Failed to change directory" error and a silent exit 0 with no
stdout.

Root cause: detectRuntimes() returned `bun ?? process.execPath` for
the javascript runtime (src/runtime.ts:253). PR #190 (f69b0d2)
introduced the execPath default to avoid the snap-Node wrapper
re-invocation problem, but assumed execPath always points at a JS
runtime — false for in-process plugin hosts whose execPath is the
host binary itself.

Fix: extract resolveJavascriptRuntime() helper that gates execPath
on the existing JS_RUNTIMES allowlist (src/adapters/types.ts:421 —
the same single-source-of-truth set PR #708 introduced for
buildNodeCommand). When execPath basename is not in {node, bun,
deno}, fall back to commandExists("node") ? "node" : null. The
allowlist is cross-OS by design — strips optional .exe and splits
on both separators, so the bug reproduces and fixes identically on
macOS, Linux, and Windows (the reporter only saw the Windows shape
but the cross-OS check is correct).

Preserves PR #190 snap-Node behavior: snap wrapper's binary is
literally named `node` → in JS_RUNTIMES → execPath returned
verbatim. Covered by regression test "snap-node host".

When neither bun nor PATH node is reachable, runtimes.javascript
is null. RuntimeMap.javascript is widened to string | null;
getRuntimeSummary surfaces an actionable "not available" line
instead of literal "null", and buildCommand throws a clear error
before spawning the wrong binary. server.ts:3895 jsRuntime
forwarding is null-guarded (downstream buildNodeCommand already
defaults to "node" when jsRuntime is omitted).

Tests added (tests/runtime.test.ts):
- Windows opencode.exe host falls back to PATH node
- POSIX opencode binary host falls back to PATH node (cross-OS)
- null when host is non-JS and node missing
- snap-node host preserves execPath (regression for #190)
- bun host preserves execPath
- doctor summary surfaces actionable error when javascript is null

Archaeology:
- f69b0d2 (#190) — introduced bun ?? process.execPath default
- PR #708 — added JS_RUNTIMES + IN_PROCESS_PLUGIN_PLATFORMS

…brew Cellar ENOENT (#800) (#803)

* fix(runtime): add liveness guard to resolveJavascriptRuntime for Homebrew Cellar ENOENT (#800)

When process.execPath is a Homebrew Cellar path
(/opt/homebrew/Cellar/node/VERSION/bin/node), brew upgrade
plus brew cleanup deletes the old Cellar directory, leaving the
in-process execPath dangling.  The liveness guard falls back to
PATH-resolved node when the execPath no longer exists on disk.

Preserves the snap-node fix (#190): the snap wrapper binary
literally exists at its execPath, so the guard passes and the
path is returned verbatim (not collapsed to bare node).

- Add existsSync(execPath) check before returning execPath
- Existing snap-node + bun regression tests updated to mock
  existsSync returning true for their respective exec paths
- Two new tests covering:
  1. Stale Cellar path falls back to PATH node
  2. Stale Cellar + no PATH node returns null

* fix(test): cross-platform bun path mock in #800 Cellar ENOENT test

The existsSync mock only blocked Unix-style bun paths
(/.bun/bin/bun), but on Windows bunFallbackPaths returns
paths with backslashes (C:\Users\...\.bun\bin\bun.exe).
This caused bunExists() to find a real bun on the Windows CI
runner, making resolveJavascriptRuntime return the bun path
instead of 'node'.

Replace the single-platform .includes() check with a
cross-platform regex that matches both file separators
and the optional dot prefix on ~/.bun.