feat: add list-cwd action to scope peer discovery by working directory

[iRonin]

What

Adds an intercom({ action: "list-cwd" }) action that lists only the sessions sharing the caller's working directory — the scoped-discovery default an orchestrator usually wants — while list stays all-directories. An optional cwd narrows to a specific directory (absolute, or relative to the caller's cwd; "." means the current cwd).

Why

When several pi sessions run on one machine across different projects, list returns every peer regardless of directory. A coordinating agent almost always wants just the peers in the current working tree.

Doing that with a raw s.cwd === currentCwd string match is subtly wrong — it hides genuine same-directory peers whose cwd string differs only by:

• a trailing slash (/work vs /work/),
• a . / .. segment, or
• a symlink (on macOS /tmp ↔ /private/tmp, or any symlinked project root).

So the new cwd.ts normalizes both sides before comparing — resolve() for the lexical variants and realpathSync() for symlinks (best-effort, with a graceful fallback if the directory no longer exists; memoized since the set of distinct cwds is small and stable).

Small robustness touch: if you filter by a directory that has no peers while your own cwd does (easy to do by passing a guessed parent path), the empty result points back to your real cwd and its peer count instead of a silently misleading "no sessions".

Scope

Purely additive — a new action mirroring list, reusing the existing formatSessionListRow and result conventions. Zero behavior change to list / send / ask / reply / pending / status.

Design note

I chose a separate list-cwd action over adding a cwd filter to list, for explicitness and back-compat (existing list callers and output are untouched, and the intent reads clearly at the call site). Happy to refactor into a list filter instead if you'd prefer a single action.

Tests

New cwd.test.ts covers normalizeCwd / sameCwd: trailing slash, lexical ./.. collapse, symlink resolution (real fixture), and the missing-dir fallback. Full suite green (96/96, including the 5 new).