feat: add transactional recipe founder path

[davidahmann]

Outcome

Adds Mill's first transactional founder path from approved product contracts to an exact, reviewed draft-PR candidate, while preserving explicit human authority for consequential decisions and merge.

What changed

• adds one exact Node.js 24, TypeScript, Next.js 16, React 19 recipe and behavior-specific browser oracle
• adds deterministic greenfield and compatible-adoption plans with separate attended apply approval
• adds lock-bound dependency preparation and networkless, source-read-only OCI verification
• adds continuity-bound task compilation plus run next, start, ship --draft, and detach-planning workflows over the existing lifecycle
• hardens exact-base Git reads, UTF-8 identity, crash-released leases, cancellation, and two-phase greenfield authority publication
• aligns schemas, runtime contracts, documentation, negative cases, package validation, and same-change task closure
• keeps Mill standalone: no tracked Factory profile, verifier, pack, sibling checkout, or runtime dependency

Validation

• npm run check under repository-pinned Node 24.20.0: 23 files and 166 tests passed; branch coverage 80.18%
• rendered recipe installed from its exact lock and passed format, lint, type, unit, integration, Playwright browser, build, and package checks offline in the pinned Playwright OCI image
• greenfield cancellation passed 20 final-publication-boundary stress runs and 30 commit-boundary stress runs
• exact-candidate local Codex review completed with no material findings
• clean exact candidate: 5d3851043f61eab1e3895b1e2e785e3ecbe96c08

Deliberate limits

This does not add autonomous specification generation, arbitrary-stack support, remote repository creation, automatic readiness or merge, deployment, release, daemon operation, or a hosted control plane.

[davidahmann]

@codex review

[davidahmann]

@codex review