Scope ambient policy to supported surfaces

[time-attack]

Summary

• keep web-project standing orders available for addressed turns while removing unsupported ambient/bot controls from member and admin editors
• derive policy applicability on the server and enforce it consistently across member, admin, and agent-facing writes
• reject unsupported web-project ambientEnabled/bots fields atomically without deleting legacy values or history
• make web-project tool guidance and the composed autonomous-mode prompt explicitly addressed-only while preserving Slack autonomous behavior

Fixes #317.

Test plan

• prompt/resolution/orchestrator suites: 190 passed
• policy/project/auth/core suites: 382 passed
• web UI suites: 32 passed
• admin plugin suites: 114 passed
• root, web UI, admin, CLI, and contract typechecks
• targeted ESLint, Oxlint, Prettier, and git diff --check

The tests cover orders-only save/read and prompt use, atomic rejection, legacy preservation, stale UI responses, full composed prompt semantics, and Slack channel/group-DM controls.

---

^{Need help on this PR? Tag @codesmith-bot with what you need. Autofix is disabled.}