M7: tiers 2 to 4

[tamnd]

Tiers 2 through 4. Spends model calls.

Root pages, faq/, installing/, distributing/, deprecations/, reference/, howto/, using/, extending/ and c-api/. Roughly 18 604 entries and 695 batches.

Checklist

• Run tier 2, audit, sample at 5 %, review, fix
• Run tier 3, the same way
• Run tier 4, c-api/, only after the glossary has absorbed tiers 2 and 3
• Glossary bumps, with the stale --glossary re-queue path exercised for real
• G01 through G06 promoted from soft to hard
• Delete the old MACHINE/ tree, with its final numbers recorded in reports/quality.md first

Exit

Tiers 1 through 4 complete and audited. Glossary adherence at or above 95 %. The stale --glossary path has been used at least once on a real bump, and the set it re-queued was the affected entries rather than the corpus. Coverage table in the README, H06 passing.