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.

server/lib/pipelines.js

@@ -40,6 +40,16 @@ function loadAll() {
           label: n.label || n.id,
           icon: n.icon || "",
           gate: !!n.gate,
+          // The one command that drives THIS node — a slash command
+          // (`/superpowers:writing-plans`) or a shell one (`ccam lanes hook
+          // ci-gate`), mirroring whatever the node's own `detect` rules watch
+          // for. `doc.skill` above names the driver for the whole pipeline;
+          // this narrows it to the step, so a reader of the pipeline map can
+          // see what actually moves each node instead of inferring it from a
+          // regex. Empty for a node with no single driver (`done`, or a gate
+          // another agent declares). Never executed by the dashboard — it is
+          // display text, same contract as `doc.skill`.
+          command: typeof n.command === "string" ? n.command : "",
           aliases: Array.isArray(n.aliases) ? n.aliases : [],
           detect: Array.isArray(n.detect) ? n.detect : [],
         }));
@@ -122,7 +132,7 @@ function nodeStates(pipeline, lane) {
     else if (rec) state = rec.evidence ? "done" : "passed-no-evidence";
     else if (cur > -1 && i < cur) state = "passed-no-evidence";
     else state = "pending";
-    return { id: n.id, label: n.label, icon: n.icon, gate: n.gate, state };
+    return { id: n.id, label: n.label, icon: n.icon, gate: n.gate, command: n.command, state };
   });
 }