#10265 docs(tui): add release-scope protocol metadata

Summary

• layer PR #10242 protocol-v12 inventory/prose metadata onto cumulative TUI candidate #10253
• layer PR #10241 manual-nightly documentation and workflow contract onto the same candidate
• preserve both red/green commit pairs in order

Stack

Base: 51e86225ca0ed8611922b416cb0a8ca9b0fc9f3a

1. 3fd5b47512 red PR #10242 inventory contract
2. 48ca9a51b8 green PR #10242 metadata/prose
3. 52bc53eca2 red PR #10241 nightly contract
4. 12961f7a40 green PR #10241 docs/workflow

All four commits replayed cleanly with no conflict. Existing cumulative frontend docs from #10246 remain in the base.

Verification

• local inventory and SDK schema checks
• resource boundary and generated SDK checks
• 68 workflow-security contract tests
• frontend docs contract
• PyYAML parse and actionlint for spec, SDK, and nightly workflows
• exact hosted checks will run against this head

No merge, tag, package publication, build, or settings mutation was performed.

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Summary by cubic

Adds release-scope protocol metadata to cmux-tui docs/spec and makes the nightly channel manual-only. Old: nightly ran on a daily schedule and manual dispatch, inventory tracked v10 with a pending terminal-shortcuts head; New: manual-dispatch only and inventory tracks private protocol v12 with no pending heads.

• Updates cmux-tui/spec/inventory.json to v12 for mux-control and mux-events; clears pending_heads.

• Aligns cmux-tui/spec/programmability.md to v12, removes the “explicit clear-history operation” requirement, and records that PR 8698’s shortcut and clear-history work is included.

• Documents manual-only nightlies in cmux-tui/dist/RELEASING-TUI.md; clarifies that each dispatch builds and publishes a fresh run.

• Ensures .github/workflows/cmux-tui-nightly.yml uses workflow_dispatch only; no schedule.

• Adds tests that enforce protocol-domain/version alignment, remove the pending 8698 reference, and require manual-only nightly behavior across workflow and docs.

• Required action: Trigger cmux-tui nightly manually from main when a prerelease package is needed.