feat(lanes): give every pipeline node its own driver command

A pipeline template named ONE command for the whole run (`skill`), so the
only way to know what actually moves a given node was to read that node's
`detect` regexes. Each node now carries its own `command`: a slash command
(`/superpowers:writing-plans`) or a shell one (`ccam lanes hook ci-gate`),
whichever its detect rules already watch for.

The values are derived from each node's own detect rules, not invented —
every `ccam …` string was checked against bin/ccam.js and every
`/superpowers:*` against the installed plugin. Nodes reaching which is a
declaration rather than an action (`done`, `merged`, `reported`,
`e2e-feature-passed`, `qc-plan`) are deliberately left empty.

`pipelines.js` normalizes a missing or non-string value to "", so a
custom template written before this field keeps loading rather than
rendering "undefined". `nodeStates()` and GET /api/lanes/pipeline-stats
pass it through. Never executed by the dashboard — display text, the same
contract `skill` already had.

Surfaced where each view has room for it: the Workflows pass-rate panel
shows it under the node label and copies it on click; PipelineMap folds
it into the node tooltip, because a 16-node pipeline has to fit across
one card and there is no width for a second line.

`command?: string` is optional in the client type only to spare four
unrelated test fixtures — the server always sends the key, and the UI has
to branch on the empty string regardless.

Verified: npm run test:server (1373, +3), npm run test:client (459, +2),
tsc --noEmit, prettier and check-headers clean. docs/LANES.md § Custom
template format documents the field. openapi.yaml needs no change: the
lane payload and pipeline-stats were never schematized there.

docs/LANES.md

@@ -744,11 +744,11 @@ Create a JSON file in your custom pipeline directory (e.g., `~/.ccam/pipelines/m
   "name": "ML Training Pipeline",
   "skill": "/my-training-skill",
   "nodes": [
-    { "id": "data",      "label": "data",      "icon": "📊", "gate": false, "aliases": ["intake"] },
-    { "id": "preprocess","label": "preprocess","icon": "⚙️", "gate": false, "aliases": ["prepare", "clean"] },
-    { "id": "train",     "label": "train",     "icon": "🧠", "gate": false, "aliases": ["training", "fit"] },
-    { "id": "eval",      "label": "eval",      "icon": "📈", "gate": true,  "aliases": ["evaluate", "metrics"] },
-    { "id": "deploy",    "label": "deploy",    "icon": "🚀", "gate": false, "aliases": ["ship", "release"] }
+    { "id": "data",      "label": "data",      "icon": "📊", "gate": false, "command": "dvc pull",          "aliases": ["intake"] },
+    { "id": "preprocess","label": "preprocess","icon": "⚙️", "gate": false, "command": "make preprocess",    "aliases": ["prepare", "clean"] },
+    { "id": "train",     "label": "train",     "icon": "🧠", "gate": false, "command": "/my-training-skill", "aliases": ["training", "fit"] },
+    { "id": "eval",      "label": "eval",      "icon": "📈", "gate": true,  "command": "make eval",          "aliases": ["evaluate", "metrics"] },
+    { "id": "deploy",    "label": "deploy",    "icon": "🚀", "gate": false,                                  "aliases": ["ship", "release"] }
   ]
 }
 ```
@@ -763,6 +763,7 @@ Create a JSON file in your custom pipeline directory (e.g., `~/.ccam/pipelines/m
   - **label** (string, optional): display name in the UI; defaults to `id` if omitted
   - **icon** (string, optional): unicode emoji or single character shown before the stage name
   - **gate** (boolean, optional): `true` if this stage blocks unless explicitly passed; defaults to `false`
+  - **command** (string, optional): the one command that drives THIS stage — a slash command (`"/superpowers:writing-plans"`) or a shell one (`"ccam lanes hook ci-gate"`). Where `skill` above names the driver for the whole pipeline, this narrows it to the step, so a reader of the pipeline map sees what moves each node instead of inferring it from the node's `detect` regexes. Omit it (or leave it empty) for a node with no single driver — a terminal `done`, or a gate another agent declares. Surfaced in the node's tooltip on a lane card and as copyable text per node on the Workflows page; **never executed by the dashboard**, same contract as `skill`.
   - **aliases** (array, optional): alternative names for the stage (e.g., `["training", "fit"]` lets you call `ccam stage training`)
 
 Then set the environment variable: