feat(agent): RSS-first coding tools and auth foundation - #2

Summary

This PR is organized into 14 scope- and milestone-level commits:

1. Coding-tools delivery plan
2. Tool registry and immutable run toolsets
3. Confined native file/process execution
4. Durable serial provider loop
5. RSS-tools and production-auth roadmaps
6. Scoped generic capability lifecycles
7. RSS file read/search
8. RSS file mutation
9. RSS process and dispatch ownership
10. RSS compilation and lifecycle isolation
11. Bounded RSS-first config and policy handles
12. Encrypted generation-aware credential store
13. Generic OAuth and device-flow primitives
14. Task 3 plan seal

Security properties

• Run-scoped, generation-bound, bounded capability tokens with fail-closed replay, expiry, cancellation, and restart behavior.
• Host-owned credential and OAuth secrets excluded from VM-visible values, JSON, logs, and debug output.
• Bound transport authority, path, headers, form ownership, generation, run identity, deadlines, and single-flight consumption.

Verification

• cargo fmt --all -- --check
• cargo check --workspace --all-features
• cargo clippy --workspace --all-features --all-targets -- -D warnings
• cargo test --workspace --all-features --all-targets
• Focused config/auth/OAuth/RSS, gateway, capability, file/process, and architecture suites

The curated branch has the exact same final Git tree as the previously verified integration head.