Add a time-of-day race day schedule to Event Manager

Events can now be given a start time and a gap between sessions on a
new "Schedule" panel; every session's planned clock time cascades
automatically in running order (practice, qualifying, finals), and
once a session actually starts or finishes, everything after it
re-anchors to that real time - a late start or a session that ran
long (including any pause) pushes the rest of the day forward with
no manual reschedule step. The scheduled time now also shows on the
printed/PDF start lists.

Printable start lists and manually moving a driver to start last in
their own heat (for a mechanic-time request) already existed, so
this only builds the missing piece: the schedule itself.

Also fixes a real pre-existing bug in the same session-ordering logic
this feature relies on: getSessionSortWeight used `order[type] || 99`,
which silently treated open_practice's own weight of 0 as falsy and
sorted practice sessions dead last instead of first in print/PDF
output.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

ROADMAP.md

@@ -367,6 +367,23 @@ Reported 2026-09-10 by the user: the "select session" dropdown (Timing) and the
 
 Verified 2026-09-10 with a live headless-browser check against a real, isolated server: seeded 3 events with a mix of practice/qualifying/final sessions and confirmed the rendered `<select>` groups them into 3 correctly-labeled, newest-first `<optgroup>`s with each event's own sessions nested inside.
 
+## Time-of-day race day schedule
+
+Requested 2026-09-10 by the user: when running a race day, should be able to set it up as time-scheduled - start Practice 1 at 12:34, and once it's done the next session (with drivers) is automatically set to start e.g. 3 minutes later at 12:42, and so on; must be pausable if something goes wrong, printable start lists, and a driver who's TQ in a qualifying heat but needs to request work time on their car should be able to start last in that heat instead.
+
+Investigated first and confirmed two of the three pieces already existed, before building the missing one:
+- Printable/PDF start lists already existed (`events.print_startlists`/`events.pdf_startlists` in Event Manager).
+- Manually moving a driver to start last in their own heat already existed via the drag-and-drop grid editor (`gridDragList` in `event_manager_controller.js`, reordering `session.manualGridIds`) - already covers the "request mech time, start last" scenario without any new work.
+
+Built the genuinely missing piece, confirmed with the user before starting given its size:
+- [x] `buildEventSchedule` (`src/event_race_logic.js`, new) computes each race-mode session's planned clock time in running order (reusing the same `getSessionSortWeight` ordering the print/PDF output already uses: practice, then qualifying, then finals), cascading from a configured day-start time plus each session's own duration/follow-up plus a configurable gap between sessions. Once a session has actually started or finished, everything scheduled after it re-anchors to that real time instead of the original plan - a late start or a session that ran long (a paused session's real `endedAt` already reflects the full wall-clock time it took) automatically pushes the rest of the day forward with no separate "reschedule" action, which is what covers "must be able to pause" without any extra pause-specific schedule logic.
+- [x] New "Schedule" panel in Event Manager (`src/event_manager_view.js`/`event_manager_controller.js`): a start-time + gap-between-sessions form, and (once set) a table of every session with its planned time range, its real start/end once it has one, and a "Delayed" flag for a session that started more than a minute late. New `event.raceConfig.scheduleStartAt`/`scheduleGapMin` fields, added to `normalizeEvent`'s explicit field allowlist (an event's `raceConfig` is fully rebuilt from that allowlist on every save - any field not listed there is silently dropped, caught during this work before it shipped).
+- [x] The scheduled time is now also shown on the printed/PDF start lists (`buildRaceStartListsHtml` in `src/race_render_helpers.js`) next to each session's name.
+
+Found and fixed a real, previously-existing bug while building this, unrelated to the new feature but affecting the same ordering logic: `getSessionSortWeight` (`src/race_render_helpers.js`) used `order[type] || 99` - since `open_practice`'s own weight is `0`, a falsy value, `||` silently replaced it with the 99 "unknown type" fallback, sorting practice sessions dead last (tied with genuinely unrecognized types) in the print/PDF start lists and results, instead of first. Fixed to `??`.
+
+Verified 2026-09-10: new unit tests cover `getSessionSortWeight`'s fix directly, and `buildEventSchedule`'s cascading math, the running-order sort, track-mode sessions being excluded, and the re-anchoring behavior for both a late-but-still-running session and a finished one whose real duration (including a pause) differed from the plan. A full headless-browser run against a real, isolated server reproduced the exact reported workflow: set a 12:34 start time with a 3-minute gap on a real Open Practice + Q1 H1, confirmed the schedule panel showed practice at 12:34-12:39 and qualifying at 12:42-12:47, confirmed the printed start list included "12:34" next to Open Practice, then made practice actually start 2 minutes late and confirmed the panel flagged it "Delayed" and qualifying's planned time shifted forward to 12:44 automatically.
+
 ## Documentation maintenance
 
 - [ ] Update the architecture's module/dependency inventory as modules change.