docs(oat): add backlog alignment and project planning map

[tkstang]

Summary

• Capture the scope/provider, review/gate, and bookkeeping backlog priorities and link them to the relevant OAT projects.
• Promote agent-provider-root to spec-driven and add its starting-point discovery, specification, and design artifacts.
• Add the project grouping tree, workflow-mode recommendations, dependency map, and explicit concurrent kickoff lanes to the roadmap and priority alignment.

Backlog and project coverage

This covers the active scope/provider cluster, the review/gate integrity cluster, the ReviewPlan workflow, and the two standalone gate contracts. The complete ID-and-title mapping is recorded in .oat/repo/pjm/roadmap.md and .oat/repo/pjm/backlog/reviews/priority-alignment.md.

Validation

• Push checks passed: release:check-versions, type-check, lint, and format.
• pnpm exec oxfmt --check passed for the changed Markdown artifacts.
• git diff --check passed.
• oat pjm doctor --json confirms repository adoption is declared; it reports only existing PJM layout warnings.
• The local commit hook reports the known missing control-plane/dist module before the build restores it; the push completed successfully.

[cursor]

PR Summary

Low Risk
Documentation and OAT project metadata only; no application code, config defaults, or release artifacts are modified in this diff.

Overview
Adds and refreshes OAT project lifecycle documentation so backlog themes map to concrete discovery/spec/design work, without changing CLI or runtime behavior.

agent-provider-root is promoted from quick discovery to spec-driven design: new spec.md and a full design.md define per-dependency canonical agent-root binding, portability ratchet for bare .agents/agents/ reads, consumer migration, and boundaries with tool-pack-scope-provider-truthfulness. state.md now tracks design phase, linked backlog/project issues, and draft spec/design artifacts; discovery.md gains an explicit revalidation notice.

New or expanded discovery dossiers (with plan/implementation templates where noted) capture bounded follow-ups: gate-headless-no-yield (headless gate children must not background required work; cause-specific diagnostics vs PR #190), gate-structured-output-contract (warn when configured oat gate review omits global --json), review-gate-integrity (grouped backlog: bookkeeping-only non-re-review, source-qualified receipts, gate event binding, closeout freshness), and tool-pack-scope-provider-truthfulness (scope vs placement vs provider visibility, directory symlink adoption, init/AGENTS.md guidance; boundary with agent-provider-root after PR #231).

review-plan-workflow discovery now states it is a non-exhaustive baseline that must be revalidated before plan approval.

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