docs: replan v0.11 and v0.12 roadmap

[screenleon]

Summary

• replace the skipped v0.14.0 public-contract milestone with contiguous v0.12.0
• preserve the existing v0.11.0 Phase 1–9 delivery history and remaining scope
• append new v0.11 work as Phase 10–12 instead of replacing earlier phases
• add CC-530 through CC-533 as the new runtime-authority/Gate priorities
• preserve the remaining architecture recommendations as CC-534 through CC-539 someday backlog tickets
• record that milestone replanning must retain existing delivery history while avoiding unrelated archive resurrection
• leave BACKLOG-ARCHIVE.md unchanged

Why

The roadmap should move contiguously from v0.11.0 to v0.12.0, but MILESTONES.md also serves as the delivery record for work already completed within v0.11.0. New architecture work therefore belongs in later phases after the existing Phase 1–9 content; it must not replace that history. Non-blocking recommendations remain explicitly tracked in BACKLOG without becoming v0.11 release blockers.

Impact

Documentation and planning only. No runtime, CLI, schema, test, or installation behavior changes.

Validation

• pm/scripts/validate.sh BACKLOG.md DECISIONS.md CHANGELOG.md
• tests/bin/run-tests.sh --base main — 4 passed, 0 failed
• git diff --check
• main-versus-branch v0.11 ticket-row comparison — no original rows removed
• tools/lint/check-docs-freshness.sh — 0 blocking findings; 3 pre-existing pr:TBD warnings outside this diff

No PR gate or authoritative full suite was run for this docs-only planning update.