fix(tools): preserve live session cwd in terminal_tool, keep ACP update_cwd authoritative

[kshitijk4poor]

Summary

Salvage of #35510 by @Dusk1e — fixes a terminal_tool cwd regression for existing sessions, with one additional fix so the ACP update_cwd path stays authoritative.

When a session had already changed directories, terminal_tool() could still force later commands to run in the init-time/config cwd instead of the live session cwd. That caused both foreground commands and background launches to run in the wrong directory.

Fix

• Added a small cwd resolver in tools/terminal_tool.py with this precedence:
  1. explicit workdir
  2. live session env.cwd
  3. fallback config/init cwd
• Applied that resolver to:
  • foreground env.execute(...)
  • background process_registry.spawn_local(...)
  • background process_registry.spawn_via_env(...)
• Preserved existing explicit workdir behavior.

Additional fix vs #35510

Preferring live env.cwd (so a session-local cd survives) means a freshly registered cwd override would otherwise sit below the already-set env.cwd. The ACP adapter sets the editor's working directory exclusively through that override — acp_adapter/session.py::_register_task_cwd → register_task_env_overrides(task_id, {"cwd": ...}), called on session/load and session/resume (acp_adapter/server.py). With the override demoted below env.cwd, an editor's mid-session project-root change would be silently ignored once any command had run in a long-lived ACP server process.

register_task_env_overrides now syncs a newly registered cwd onto the live cached env, so:

• an explicit ACP update_cwd wins (the editor's project root takes effect), and
• ordinary in-session cd tracking is still preserved (no override re-registration → env.cwd is left to the cd machinery).

Testing

tests/tools/test_terminal_task_cwd.py
7 passed

Regression coverage:

• existing task cwd override behavior
• explicit workdir override behavior
• foreground commands following live env.cwd
• background commands following live env.cwd
• registering a cwd override updates the live env cwd (ACP authority)
• no-op when no live env exists yet
• non-cwd overrides (e.g. per-task Modal image) leave env.cwd untouched

ruff check clean; no new ty diagnostics in the changed region.

Based on #35510 by @Dusk1e.

[alt-glitch]

Salvage of #35510 by @Dusk1e. Adds ACP update_cwd authoritativeness fix on top of the original CWD precedence fix.