fix(runtime): prepare v0.9.19 hotfix

[spytensor]

Summary

Closes #398.

• Retry stale Codex resume thread ids once with a fresh Codex thread instead of rendering raw Session not found for thread_id text as @host output.
• Make @user visibly distinct in scrollback by using the prompt green identity color.
• Suppress the root host TurnDispatched banner so normal user -> host turns do not double-label @host, while preserving real cross-role handoff banners.
• Bump release metadata to v0.9.19: Cargo, npm wrapper, docs.rs URL, README direct install tag, splash copy, CHANGELOG, and boot dashboard snapshot.

Changed files

• src/adapter/codex.rs: stale Codex session detection/retry and tests.
• src/repl/render.rs, src/repl/tests.rs: suppress root host dispatch banner and cover it.
• src/console_room_runtime.rs: visible @user identity color.
• Cargo.toml, Cargo.lock, src/lib.rs, npm/package.json, README.md, data/splash_content.toml, CHANGELOG.md: v0.9.19 release metadata.

Acceptance criteria

• Stale Codex resume ids retry fresh once instead of surfacing raw adapter text.
• @user scrollback label is visibly styled.
• Root host turns no longer render a duplicate host handoff banner.
• v0.9.19 release metadata is prepared.

Validation

• cargo fmt --all -- --check
• git diff --check
• env -u NO_COLOR TERM=xterm-256color cargo test --quiet — 765 passed, 1 ignored in lib; smoke tests intentionally ignored.
• cargo clippy --all-targets --all-features -- -D warnings
• cargo build --release
• python3 scripts/dogfood-v09-user-cases.py — cr 0.9.19, DOGFOOD PASS: v0.9 local user-case gate completed.

Evidence packet

Local project evidence showed .coreroom/sessions/ids/host.id contained 4028d717-299e-4039-b333-c615a041c197, and .coreroom/messages.jsonl recorded the same stale id followed by an @host role_spoke event containing Session not found for thread_id: 4028d717-299e-4039-b333-c615a041c197. That made the root cause a stale Codex resume id being returned as tool text, not a new user thread.

Risks and remaining gaps

• The stale-session detector intentionally matches exact leading Session not found for thread_id: text or a JSON-RPC message field with that leading text. If Codex changes the wording, it will fall back to the existing error path.
• This does not clear stale ids before the next successful retry; it relies on the successful retry's RoleSessionUpdated event to persist the fresh Codex thread id.

Rollback plan

Revert this commit and release a corrective patch tag if the retry path regresses Codex session continuity or if the transcript rendering change hides a required handoff banner.

Tracker update

No milestone tracker update required; this is a direct v0.9.18 -> v0.9.19 maintainer hotfix tracked by #398.