fix(lanes): stop archive/activate from clobbering feature title and links

archiveActiveFeature was overwriting a feature's own title with the
LIVE lane's title on every clear/switch — a --title set on activation
silently disappeared. activateFeature restored stage/status/gate/CI/
stages/notes onto the live lane when switching back to a past feature,
but never links, so they vanished on reactivation. Both are fixed, with
a regression test for each (full activate/archive/reactivate round trip
for links).

Also fixes server/routes/lanes.js: the doc comment explaining GET
/:id/git's rationale had been left sitting above the newly-inserted
/:id/features routes instead of its own route.

docs/API.md's Lane features section described fields and behavior that
don't exist in the real routes (an "active" boolean, a POST response
containing "archivedPrevious", a "409 ESTALE" concurrency response) —
rewritten to match the actual request/response shapes exactly.

docs/API.md

@@ -400,76 +400,71 @@ with no slot returns `{"available": false}`.
 
 #### Lane features
 
+Per-feature state and archive (`server/lib/lane-features.js`) — a lane's
+`stage`/`status`/etc. is always the LIVE view of whichever feature it's
+currently on; these routes read and switch between a lane's feature history.
+
 ```http
 GET /api/lanes/:id/features
 ```
 
-List every feature this lane has activated, archived or live:
+Every feature this lane has ever activated, archived or live, most recently
+touched first:
 
 ```json
 {
   "features": [
-    { "slug": "auth-redesign", "active": true, "title": "Auth redesign (v2)", "stage": "implement", "status": "running", "created_at": 1722702012 },
-    { "slug": "migration", "active": false, "title": null, "stage": "done", "status": "idle", "created_at": 1722700000 },
+    {
+      "id": 5, "lane_id": 12, "slug": "auth-redesign", "title": "auth-redesign",
+      "branch": "feat/auth", "pipeline": "default", "stage": "implement",
+      "stage_since": "2026-08-04T09:00:00.000Z", "status": "running",
+      "gate_decision": null, "ci_status": null, "qc_dev": null,
+      "stages": {}, "links": {}, "notes": null, "archived_at": null,
+      "created_at": "2026-08-04T09:00:00.000Z", "updated_at": "2026-08-04T09:00:00.000Z",
+      "pipeline_name": "Default", "pipeline_nodes": [ /* same shape as a live lane's */ ], "progress": 40
+    }
   ]
 }
 ```
 
-Each feature carries a canonicalized `slug` (drops leading `feat/`, `/` → `-`, preserves case, keeps `[A-Za-z0-9._-]` only — **not the same rule as `worktree.js:slugify`**, which lowercases). `active` is `true` for the currently live feature. `title` is the display name (human-chosen via `ccam feature activate --title`; omitted/`null` if never set or identical to slug). `stage`, `status`, `notes` reflect the **saved** state when this feature was last archived; `active:true` shows the **live** lane's current stage instead.
+Each row is the hydrated `lane_features` row (`stages`/`links` parsed from
+JSON) plus `pipeline_name`/`pipeline_nodes`/`progress`, computed the exact
+same way a live lane's are — the client renders an archived feature with the
+same `PipelineMap` component, no special-casing. `archived_at` is `null` for
+the currently-active feature, an ISO timestamp for every past one. `slug` is
+always the **canonicalized** form (drops a leading `feat/`, turns `/` and
+whitespace into `-`, keeps `[A-Za-z0-9._-]`, preserves case — **not the same
+rule as `worktree.js:slugify`**, which lowercases everything).
 
 ```http
 GET /api/lanes/:id/features/:slug
 ```
 
-Show one feature's saved pipeline:
-
-```json
-{
-  "slug": "auth-redesign",
-  "active": true,
-  "title": "Auth redesign (v2)",
-  "stage": "implement",
-  "status": "running",
-  "notes": "Testing with OAuth...",
-  "created_at": 1722702012
-}
-```
-
-Works on both archived and active features. If the slug has never been activated, returns `404 ENOFEAT`.
+One feature by its canonicalized slug, same shape as an entry above, wrapped
+as `{ "feature": {...} }`. `404 ENOFEATURE` if that slug was never activated
+on this lane; `404 ENOLANE` if the lane itself doesn't exist.
 
 ```http
 POST /api/lanes/:id/features/activate
-{ "slug": "auth-redesign", "title": "Auth redesign (v2)" }
+{ "slug": "feat/Auth Redesign", "title": "Auth redesign (optional)" }
 ```
 
-Activate a feature by slug. Request body:
-- `slug` (required, string) — the canonicalized slug (or raw slug; the route canonicalizes it before lookup)
-- `title` (optional, string) — human-friendly name to save with this feature
+Switches the lane to a feature by slug:
+- If a **different** feature is currently active, it is archived first with
+  its exact live state (stage, status, gate/CI fields, stages, links, notes)
+  — its own `title` is never overwritten by this.
+- If the target slug was activated before, its saved state is restored onto
+  the live lane (stage, status, gate/CI fields, stages, links, notes) — this
+  is what makes switching back to a past feature resume where it left off.
+- If the slug is new, a fresh feature row is created (`title` defaults to the
+  slug itself when omitted).
+- Re-activating the **currently** active slug is a no-op.
 
-Response:
+Response: `{ "lane": <same shape GET /api/lanes/:id returns>, "feature": <same shape as the list above> }`.
 
-```json
-{
-  "slug": "auth-redesign",
-  "active": true,
-  "title": "Auth redesign (v2)",
-  "stage": "implement",
-  "status": "running",
-  "created_at": 1722702012,
-  "archivedPrevious": { "slug": "migration", "stage": "done" }
-}
-```
-
-Behavior:
-- If the target slug has been activated before, restores its saved stage/status/notes onto the live lane
-- If the slug is new, creates a fresh feature row with empty stage/status/notes
-- If a different feature is currently active, archives it first (copies live stage/status/notes to its row) — echoed in `archivedPrevious`
-- Returns **200** on success; **409 ESTALE** if another request changed the lane between read and write
-
-Status codes:
-- **200** — feature activated
-- **409** — the lane's stage changed concurrently (rare with single-session lanes)
-- **400** — missing/invalid request body
+- **200** — activated (or already active).
+- **400** `{ "error": { "code": "EBADSLUG", "message": "slug is required" } }` — missing/empty `slug`, or the canonicalized result is empty (e.g. `"feat/"` alone).
+- **404** `{ "error": { "code": "ENOLANE", "message": "lane not found" } }`.
 
 
 ### Locks