perf(process): wake waiters on background completion

[teknium1]

Summary

process(action="wait") now wakes as soon as a background process is moved to finished instead of waiting for the next 1-second polling tick.

Changes

• tools/process_registry.py: add a per-session completion event, signal it from _move_to_finished(), and have wait() block on the event with the existing timeout cap.
• tests/tools/test_process_registry.py: add a regression test proving wait() returns promptly when completion happens from another thread.

Validation

Check	Result
RED test before implementation	failed: wait() took 1.001s
Targeted regression	passed: 1 passed in 0.17s
Process wait smoke	passed: exited successfully in ~238ms including shell startup
Targeted suite	99 passed in 2.2s

Notes

• Preserves timeout, interrupt, detached-session refresh, local-exit reconciliation, and completion-consumed behavior.
• The untracked .plans/speed-optimization-audit.md is intentionally not included in this PR.

Infographic

[github-actions]

🔎 Lint report: hermes/hermes-29d12107 vs origin/main

ruff

Total: 0 on HEAD, 0 on base (➖ 0)

🆕 New issues: none

✅ Fixed issues: none

Unchanged: 0 pre-existing issues carried over.

ty (type checker)

Total: 10887 on HEAD, 10893 on base (✅ -6)

🆕 New issues: none

✅ Fixed issues (1):

Rule	Count
invalid-argument-type	1

First entries

tools/process_registry.py:1099: [invalid-argument-type] invalid-argument-type: Argument to bound method `ProcessRegistry._reconcile_local_exit` is incorrect: Expected `ProcessSession`, found `ProcessSession | None`

Unchanged: 5722 pre-existing issues carried over.

Diagnostics are surfaced as warnings — this check never fails the build.