resolveDefaultShell() returned a bare 'bash' when $SHELL was unset.
Under a daemon/GUI launch (devglide start) the process env can lack
PATH, so node-pty's posix_spawnp could not locate the bare command and
failed with 'posix_spawnp failed' when creating a shell pane on macOS.

- pickUnixShell(): resolve an absolute shell (/bin/zsh, /bin/bash,
  /bin/sh, ...), never a bare name. Mirrors the Windows branch.
- withDefaultPath(): guarantee a sane PATH in the spawn env so commands
  run inside the shell even when the parent env has none.

Both extracted as pure helpers with unit coverage in shell-config.test.ts.

devglide setup runs scripts/build-mcp.mjs, which bundled the voice MCP
with esbuild. nodejs-whisper (an optional whisper.cpp STT dependency) was
not in the external allowlist, so esbuild tried to inline it. When the
package is absent or fails to install, the build failed with 'Could not
resolve nodejs-whisper' and aborted every remaining bundle, degrading all
servers to the tsx fallback.

The voice provider already imports nodejs-whisper lazily and degrades
gracefully at runtime, so it should be external like better-sqlite3 and
node-pty rather than bundled.

fix(shell): spawn shell via absolute path on macOS/Linux

docs(chat): document chat_status and pipe orchestration tools

…r-external

fix(build): mark nodejs-whisper external in MCP bundling