docs: refresh backlog after Timeline merge

[kyleve]

Posted by an AI agent on kve's behalf.

Summary

• refresh the weekly module audit for PR feat(WhereUI): merge continuous planned Timeline stays #307, which landed after the same-day audit baseline
• re-verify Timeline backlog evidence and file the missing AX5 joined-card snapshot case
• correct the onboarding-gate boundary documentation everywhere it was repeated and archive that completed item
• refresh source and snapshot-reference counts to 704 and 490

Why

PR #307 landed after PR #308 had already published the September 6 weekly audit. This follow-up gives the same-day audit an explicit commit boundary and brings the derived report and durable backlog back in sync with main.

Review focus

• the evidence and scope of the new planned-stay AX5 coverage item
• the corrected onboarding-gate wording across source comments, tests, and the WhereUI README
• the same-day audit boundary and refreshed counts

⚠️ Breaking changes

None. Documentation, comments, and backlog state only.

Compatibility

No runtime or persisted-format changes.

Testing

• ./swiftformat --lint — 0 of 1,129 files require formatting
• ./shellcheck
• ./attribution --check — report current at 12 credits
• mise exec -- ./sync-agents
• python3 -m unittest discover -s Tools/Tests -p "test_*.py" — 64 passed
• ./snapshot-shards check — 49 suites, assigned 13/15/18/3
• inspected representative joined, separated, and AX5 Timeline references
• retained Ruby suite — 74 of 75 passed; one isolated-HOME harness check saw Apple Python emit Xcode cache/FSEvents diagnostics, while direct ./snapshot-shards --help was clean
• ./test not run because this change touches only Markdown and Swift comments