Drives src/routes/sessions.ts and src/lib/work-session.ts to 100%
stmts/branch/funcs/lines (branch was 84.12% / 83.33%).
- sessions.test.ts: added error/edge branch tests — malformed-JSON start
(400), non-numeric id on pause/resume/stop/discard (404), pause/resume of a
no-longer-active session (409), discard missing (404) + already-closed (409),
stop missing (404), and discard ownership scoping (user B → 404).
- work-session.test.ts: mapper unit tests — null insoleType, nullish
pausedSeconds → 0, null durationSeconds/notes, full-field shape with
activity/user opts, and opts defaulting to undefined.
- test/integration/worker-session-lifecycle.test.ts: the anchor lifecycle test
(start→pause→resume→stop→history→export).
No bugs found — the code was correct. The two remaining uncovered branches were
the defensive `row.pausedSeconds ?? 0` guards in resume/stop; pausedSeconds is
NOT NULL DEFAULT 0 in the schema, so the null branch is unreachable via any
route. Annotated both with `/* c8 ignore next -- reason */` (comment only, no
behavior change).