Break v3 into 16 tickets

One file per feature, in the v2 shape that worked: goal, context, design,
implementation, acceptance criteria, tests, risks, out of scope -- written before
implementing so the risks are on paper rather than walked into.

Three carry more weight than their size suggests. V3-01 ships the port's first
real migration, and since the destructive fallback is gone, getting addColumn and
a v1-database test right matters more than the feature. V3-08 forces a
routing-engine decision with ongoing cost, so it sits behind a RoutingService
interface mirroring what LocationSource did for GPS. V3-13 is not code at all --
it answers the three questions open since v2, and V3-15 may close unbuilt as a
result, which is a legitimate outcome.

Several tickets record constraints that are easy to lose: no activity picker in
front of Start, because the founding premise is press-and-go with gloves; the
Route-to-Trip foreign key must not cascade, or deleting an old plan deletes the
ride; V3-14 will deliberately break the parity harness by adding GPX <type>, and
that expectation should be updated rather than the check dropped; and V3-16 must
not regress the explicit text colours that exist because of the black-on-black bug.

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

docs/v3/README.md

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+# v3 tickets
+
+One file per feature, in the shape that worked for v2: Goal · Context · Design ·
+Implementation · Acceptance criteria · Tests · Risks · Out of scope. Written before
+implementing, so the risks are on paper before they are walked into.
+
+Menu, not a commitment. Nothing here is scheduled.
+
+**Everything in v3 is buildable with no server.** Group rides, accounts and paid cloud
+backup are v4 — see [../BACKLOG.md](../BACKLOG.md).
+
+> **Before starting anything:** [../port/REAL-RIDE-CHECKLIST.md](../port/REAL-RIDE-CHECKLIST.md).
+> The port has never recorded a real ride, and item I3 may still force a change of GPS
+> engine — which would land underneath several of these tickets.
+
+## The tickets
+
+| # | Ticket | Size | Depends on |
+|---|---|---|---|
+| [V3-01](V3-01-activity-type.md) | Activity type per ride | M | — |
+| [V3-02](V3-02-settings-screen.md) | Settings screen | S | — |
+| [V3-03](V3-03-units.md) | Distance and speed units | S | V3-02 |
+| [V3-04](V3-04-live-map.md) | Live map on the recording screen | M | — |
+| [V3-05](V3-05-mounted-mode.md) | Mounted (handlebar) mode | M | V3-04 |
+| [V3-06](V3-06-notification-stats.md) | Live stats in the notification | S | — |
+| [V3-07](V3-07-route-drawing.md) | Route drawing (pins, straight lines) | M | — |
+| [V3-08](V3-08-road-routing.md) | Road-snapped routing and ETA | L | V3-07, V3-01 |
+| [V3-09](V3-09-route-following.md) | Follow a planned route | M | V3-04, V3-08 |
+| [V3-10](V3-10-trip-splitting.md) | Trip splitting | S | — |
+| [V3-11](V3-11-offline-tiles.md) | Offline tile pre-download | M | V3-04 |
+| [V3-12](V3-12-crash-reporting.md) | Crash reporting | S | — |
+| [V3-13](V3-13-real-ride-measurements.md) | Real-ride measurements | M | **riding** |
+| [V3-14](V3-14-gpx-interop.md) | GPX interoperability | S | V3-01 |
+| [V3-15](V3-15-auto-pause.md) | Auto-pause | M | V3-13 *(gated)* |
+| [V3-16](V3-16-visual-identity.md) | Visual identity | M | V3-04, V3-05 |
+
+## Dependencies
+
+```
+V3-01 ──┬────────────► V3-08 ──► V3-09
+        └──► V3-14           ▲
+V3-07 ──────► V3-08          │
+V3-02 ──► V3-03              │
+V3-04 ──┬──► V3-05 ──┬───────┘
+        ├──► V3-11   └──► V3-16
+        └──► V3-09
+V3-13 ──► V3-15  (gate: may close unbuilt)
+
+no dependencies: V3-01 · V3-02 · V3-04 · V3-06 · V3-07 · V3-10 · V3-12
+```
+
+## Three that carry more weight than their size suggests
+
+**V3-01** ships the port's **first real migration**. The destructive fallback is gone, so
+getting `addColumn` plus a v1-database test right matters more than the feature does —
+V3-07 and V3-09 both add migrations behind it.
+
+**V3-08** forces a routing-engine decision with ongoing cost and vendor implications.
+Behind a `RoutingService` interface, mirroring what `LocationSource` did for GPS.
+
+**V3-13** is not code. It answers the three questions that have been open since v2, and
+**V3-15 may close unbuilt** as a result — a legitimate and probably likely outcome.
+
+## Suggested order, if starting cold
+
+1. **V3-01** — proves the migration path while the stakes are low, and unblocks V3-08/14
+2. **V3-02 + V3-03** — small, self-contained, gives V3-01 a home
+3. **V3-04** — the most visible change, and the gateway to four other tickets
+4. **V3-07** — entirely independent; useful on its own before the routing decision
+5. **V3-13** — as soon as there is a ride to measure
+
+V3-12 is a good filler at any point. V3-16 should wait until the screens stop moving.