docs(pointers): close open pointer findings in harness-config, instruction-placement and machine-health #8007

Refs: #7293

Agent Brief

Type: Task
Summary: Close the upstream-pointer sweep's open medium and low findings in harness-config, instruction-placement and machine-health.

Current behavior:
The sweep's light pass (#7293) left these findings open as of 2026-10-11/12:

• harness-config agents-md-liveness: incomplete-record, plugins/mods/overview#mods-built-into-claude-code
• harness-config gap-analysis: incomplete-record, plugins/mods/overview#compare-mods-settings-hooks-skills-and-mcp-servers
• harness-config unhobble SKILL.md: missing-pointer, headless#start-faster-with-bare-mode
• harness-config audit-instructions criteria (recheck): incomplete-record sub-agents#what-loads-at-startup; drift and incomplete-record features-overview#understand-how-features-layer; wrong-host citation for the context-engineering blog post
• instruction-placement migrate sources: incomplete-record, plugins/create
• machine-health Windows check catalog: drift, interactive-mode#how-backgrounding-works

Desired behavior:
Each listed passage is re-checked against the live page (docs fetch scripts). A finding already fixed on main is left alone and noted in the PR body. Otherwise: drift is corrected to what the live page says now; a missing pointer gains a pointer record (exact anchor, as-of date, recheck trigger); an incomplete record gains its missing parts; a wrong-host citation names the canonical URL. Restated volatile specifics in skill bodies become pointers, not new copies.

Key interfaces:

• Pointer records: anchor, as-of date and recheck trigger beside each restated upstream fact.

Acceptance criteria:

• Each listed finding is either changed in the diff or named in the PR body as already fixed, with the live anchor it was checked against.
• Every pointer record the diff adds or completes carries an anchor, an as-of date and a recheck trigger.
• check-skill.sh passes on every skill whose files the diff touches. (skip if no skill file is touched)
• scripts/check-changelog-fragments.sh passes, with one changelog fragment for each plugin the diff touches. (skip for repository-root files)

Out of scope:

• High-severity findings (not in Light pointer pass: open medium and low pointer findings from the upstream-pointer sweep #7293).
• Files outside this group.
• Vendored upstream baselines (playbooks boris vendor/upstream-skill.md).

This was generated by AI during backlog shaping. Split from #7293; the owner approved filing it in an attended backlog-shaping session on 2026-10-18.