docs(repo): epic 1 retrospective and story rows to done

[jundymek]

What this is

Supervisor deliverables for Epic 1, opened from supervisor/epic-1-workspace-scaffold because they are the supervisor's own work rather than any story's: routing them through a finished story agent would fake their provenance. Two files, no code.

1. docs/implementation-artifacts/epic-1-contract-foundations/epic-1-retrospective.md — the epic retrospective. Delivery metrics, six post-run observations each with symptom / cause / why no story caught it / fix, technical debt carried forward, next-epic readiness, and eight action items with owners. This is the repository's first retrospective, so it also establishes where the next one goes; move it if you want a different location.

2. docs/implementation-artifacts/sprint-status.yaml — the Epic 1 rows written once at closure rather than per story. Three go to done (1.1, 1.2, 1.3). 1.4 deliberately stays review: its PR is merged, but the story's owner gate — your acceptance of the perf verdict — is still open, and that acceptance is what releases 2.5 / 3.3 / 3.5. I first wrote it as done; the codex review of that commit raised a P1 saying the lifecycle source of truth would then read "go" before the decision, which was correct. Corrected on your call, with the reason in-file. Flip it yourself when you accept the verdict. Doing it now costs nothing: every story PR is already merged, so the epic-updated nudge this commit fires reaches no agent who is still working. Mid-wave it would have bought every remaining agent a rebase and a re-review.

Note this project ships no sprint-status script (no Makefile, no scripts/), so the rows were edited by hand against the four merged PRs (#1–#4) rather than measured by tooling. The four keys are the task ids verbatim, as this file's own header specifies.

What I did NOT touch

The milestones: block — including M1's "CI green", which the maintainer's CI-skip decision deviates. Reconciling a milestone definition is the owner's call and it is action item 6 in the retro.

Pending owner, carried from the closure review

1. The merge click on this PR, and then on the epic → master integration PR (which I will open once this one lands, so the base receives the status rows).
2. Acceptance of the 1.4 perf verdict — VERDICT: canvas-2d viable (>= 55 fps sustained in phases b and c). Story 1.4's task 7 requires it to stay unticked by the agent; it is unticked. Accepting it freezes 2.5, 3.3 and 3.5 against this mechanism, so it is a decision rather than a formality.
3. The six unticked steps in docs/dev/epic-1/1.4-perf-spike/MANUAL_TESTING.md — the owner's eyeball pass over the spike.
4. The M1 "CI green" wording above.

None of these is marked passed anywhere.

Verification

docs/ only; no code, no test surface. The epic head this branch fast-forwards from (41fb746) was verified in full by me at closure: pnpm lint clean, pnpm typecheck clean across six packages, pnpm test — contract 103, viz 50, scanner 2, deps 2, githist 2, cli 2 = 161 tests, 0 failures — and pnpm build producing both the tsup binary and the 131.25 kB browser bundle. This commit changes none of it.

Refs: epic-1-contract-foundations
Agent: superman (terminal-agents, claude-opus-5)