[Birfy]

Fixes #358

Docs-only: adds the user-scenario matrix the issue asks for and points the live-e2e subsystem doc at it.

What changed

• docs/testing/user-scenarios.md (new). One table, columns ID / Scenario / Persona / Surfaces / Plugins / Today / Nightly target / Blocked by, with every row the issue lists: P1–P8, X1–X2, T1–T5.
• docs/subsystems/live-e2e.md. One paragraph linking the matrix, saying the suite is one column of the map, not the map's owner.
• core/dev/eval/specs.mjs: no edit needed. Its journey fields already are the P-ids of the rows it scores (P3-tree-split, P4-invite-approve, P6-timeline), so the id sync the spec asks for already holds at this tip. Say the word if the empty sync should be recorded as a comment there anyway.

Deliberately left to the owner

The Nightly target column is not decided here: every cell reads TBD (owner decides), with the proposal from #358 in parentheses where the issue made one. Which journeys go to Nightly and which to live E2E is the owner's call, per the Lead's direction; the column can be signed in one pass without this PR having invented a decision.

Today never claims coverage without a pointer: each cell is a test file, .github/workflows/live-e2e.yml, core/dev/eval/specs.mjs, or none. T-rows carry Blocked by (#349/#352/#353/#355) instead of guessed coverage.

What I ran

Nothing locally. This host currently has no usable sandbox backend — every shell command is refused (workspace-write … no sandbox backend is usable on this host; refusing to run the command unconfined), so npm run verify and every test suite run in CI on this PR, not here. Both commits were written through the GitHub API, not git.

Not run

npm run verify, npm test, the smoke test, arch-docs — all left to CI. No source code changed, so the "revert the source change and the new test goes red" rule does not apply to this PR; the evidence is the table plus its pointers.

Scope is docs-only and stays inside the files named in the spec (6313169588), except specs.mjs, which needed no change.

[Birfy]

Verdict: PASS at 1279986

Tip SHA: 127998631a3e2f98ba2abbc405cc6e4935d52d7e
CI at this tip (run 39583278363): all 8 checks success —
  tests-ok, package, plugins (social|timeline|tree), ubuntu-latest Node 24,
  reviewed tip, risk tier
Docs-only: 2 files, +56/-0. No source change, so "revert the source change and the
test goes red" does not apply; the evidence here is the table and its pointers.

I checked every Today pointer in the new matrix against the tree at this tip rather than taking the body's word for it — all of them resolve:

• core/test/rounds.test.js, core/test/bot-tree.test.js, core/test/held-reply.test.js, core/test/face-people.test.js, core/test/authz.test.js — all present in core/test/.
• .github/workflows/live-e2e.yml and .github/workflows/nightly.yml — both present in .github/workflows/.
• core/dev/eval/specs.mjs — present, and the ids the body claims are real: P3-tree-split, P4-invite-approve, P6-timeline, each carrying the journey field the matrix references.

The page also keeps its own promises: Nightly target stays TBD (owner decides) with the issue's proposal in parentheses, Today never claims coverage without pointing at a file, and the T-rows cite Blocked by instead of guessing. That is the shape the issue asked for, and it does not invent a decision the owner has not made.

One label gap, not a code one: the PR has documentation, agent-pr, area:docs but no risk:T*. Per the label discipline every PR needs exactly one, added by the controller rather than by hand. I am not queueing this until that lands.