release: cut v0.4.0 (CHANGELOG Unreleased is complete)

[ajianaz]

What problem does this solve?

The Unreleased section of CHANGELOG.md has accumulated a full release worth of changes: tole mcp (D1), tole acp (D2), tole serve v1 (D3), the scan triages (#92/#93), the docs/standards pass (#91), gh repo auto-detect (#99), and the incoming scan-3 triage wave.

Proposed solution

1. Finish the approved hardening waves (scan-3 triage + serve hardening)
2. Bump workspace version 0.3.0 → 0.4.0, finalize CHANGELOG (date the section)
3. Tag v0.4.0 on a main-reachable commit per the release SOP (develop → PR → main → tag) — publish.yml ships both crates to crates.io

Notes

• Requires owner action for the tag/release approval per the release SOP.

[ajianaz]

Released: v0.4.0 — tag on main merge commit 6e1e9db, GitHub Release published, publish.yml succeeded (run 36866145329), crates.io verified: tole-core 0.4.0 + tole-cli 0.4.0. QA sandbox E2E passed pre-merge (run mission, serve REST auth, serve --transport mcp multi-session, acp EOF).