docs(contributor): refresh task board around v0.4.8 state

[huangruiteng]

Summary

Refreshes the public contributor task board to current main (post-v0.4.8) state without exposing private/local context.

• Archives GH-C92 (issue [Bug]: Codex CLI timeout recovery cannot resume the session observed by the failed Turn #3228 closed by fix(turn): resume preserved sessions on failed-turn retry #3262/refactor(turn): isolate failed-session recovery #3266) and GH-C93 (post-outcome memory utility attribution shipped in feat(reward-memory): attribute post-outcome utility #3280); adds lockstep stale-row guards to examples/docs-governance-smoke.py.
• Adds GH-C16 (public non-SkillsBench trajectory summary, issue [Task]: GH-C16 public-safe non-SkillsBench trajectory summary #3282) and GH-C97 (todo add --note projection fix).
• Marks GH-C68 claimed (PR test(scheduler): migrate ACK rules into decision tables #3288) and refreshes priority queue (release docs slice now targets v0.4.8 install/activation/recovery guidance).
• Updates Recent Maintainer Progress for the native-runner benchmark reset (refactor: reset benchmark research around native runners #3267), change-window gate (feat(change-window): add repository gate and pending ledger #3319), PyPI default install (feat(install): make PyPI the default complete install path #3301), community source providers (feat: add loopx-community-discussion public source provider #3299/feat(packages): add loopx-repo-health provider for public repo-health snapshots #3272), Turn recovery, quota/monitor hardening, protocol, and public docs milestones.

Validation

• git diff --check clean
• python3 examples/docs-governance-smoke.py ok
• loopx check --scan-path CONTRIBUTOR_TASKS.md --scan-path examples/docs-governance-smoke.py 0 errors, public boundary clean
• loopx canary premerge --from-git-diff 8/8 risk smokes + public boundary passed
• private-marker scan clean (no local paths, credentials, GHSA IDs, or internal context)

Type of Change

• Documentation update

LoopX Area

• Public docs or presentation surface