chore(release): prepare v0.9.20

[spytensor]

Summary

Prepare CoreRoom v0.9.20 as the patch release containing the already-merged project-truth alignment and restored live-room mouse-wheel scrollback fix.

Linked issue: none — direct user-scoped release maintenance requested in the current conversation.

Acceptance criteria

• Cargo, lockfile, npm wrapper, README direct-install tag, AGENTS release truth, and changelog all point at 0.9.20.
• Changelog has a dated 0.9.20 section and updated compare links.
• Boot dashboard snapshot version expectation matches v0.9.20.
• ANSI parser tests stay stable when the release shell has NO_COLOR=1.
• Local release dogfood exercises fresh init, fake-engine TUI, console, live-room, snapshot console, Nerd Font avatars, and README hero capture.

Changed files

• Cargo.toml, Cargo.lock — crate/package version bump.
• npm/package.json — npm wrapper version bump.
• README.md — direct binary install tag bump.
• AGENTS.md — latest release tag truth bump.
• CHANGELOG.md — 0.9.20 release notes and compare links.
• src/repl/tests.rs — boot dashboard snapshot version bump.
• src/ansi.rs — test literals for SGR parser coverage so global NO_COLOR=1 does not suppress generated ANSI before parser assertions.

Validation

• python3 scripts/check-project-truth.py
  • project truth ok: v0.9.20; active tracker guidance is not hard-coded to #238
• cargo fmt --all -- --check
  • exit 0
• cargo clippy --all-targets --all-features -- -D warnings
  • exit 0, Finished dev profile
• cargo test --all-features --locked
  • exit 0, 766 passed; 0 failed; 1 ignored; integration tests and doc-tests ok
• git diff --check
  • diff check ok
• python3 scripts/dogfood-v09-user-cases.py
  • DOGFOOD PASS: v0.9 local user-case gate completed
  • built cr 0.9.20
  • exercised cr, cr console, cr console --live-room, snapshot console, Nerd Font avatar pack, and README hero PNG verification

Evidence packet / gate

Inline evidence summary above. SDLC gate thread: th-19e67d771f0-9.

Current gate evidence records local validation and dogfood. Independent cross-model review is not satisfied in this chat-run; if proceeding, host will close the gate with an explicit accepted-risk bypass for that structural requirement after PR CI and release workflow evidence are captured.

Risks and remaining gaps

• GitHub Actions CI still needs to pass on this PR before merge.
• v0.9.20 tag/release workflow still needs to complete after merge.
• No independent current-thread cross-model reviewer was captured; this is the only known SDLC structural gap.

Rollback plan

• Before tag: revert or close this release-prep PR.
• After tag: delete the v0.9.20 tag/release only if no users have consumed it; otherwise publish a corrective v0.9.21.

Tracker update

Not applicable. AGENTS.md currently says active milestone/tracker is none; this is direct user-scoped release maintenance.