feat(schema): projects.background_md for per-project context

Phase 8c Task 1. Optional text field on projects, max 40000 chars.
The prompt module caps at 30000 with a truncation marker. Empty
documents produce byte-identical prompts to today — the test in
Task 4 locks that in.

scripts/setup-remote.ts

@@ -548,13 +548,35 @@ async function ensureActivityActionValues(pb: PocketBase): Promise<void> {
 }
 
 /**
- * Extend `cards.created_by_role` to include `"anonymous"` so the public
- * intake route can produce Inbox cards without a session. The base set
- * `["owner", "client"]` was set at first collection creation; re-running
- * `getOrCreateCollection` on an existing `cards` row is a no-op, so the
- * value set has to be patched explicitly here. Safe to re-run: values
- * are not duplicated.
+ * Extend `projects` with `background_md` so the owner can keep per-project
+ * developer context (the shape of each app, what each section does) that
+ * flows into every wizard prompt. Re-runs are safe — the field is only
+ * added if missing. Capped at 40 000 chars; the prompt module trims it to
+ * 30 000 before sending it to the model.
  */
+async function ensureProjectBackgroundMdField(pb: PocketBase): Promise<void> {
+  const projects = await pb.collections.getOne("projects");
+  const have = new Set(projects.fields.map((f: { name: string }) => f.name));
+
+  if (have.has("background_md")) {
+    console.log("  = projects.background_md already present");
+    return;
+  }
+
+  const fields = [...(projects.fields as unknown[])];
+  fields.push({
+    name: "background_md",
+    type: "text",
+    required: false,
+    max: 40000,
+    presentable: false,
+    hidden: false,
+    system: false,
+  });
+  await pb.collections.update(projects.id, { fields });
+  console.log("  + projects field: background_md (max 40000)");
+}
+
 async function ensureCardsCreatedByRoleValues(pb: PocketBase): Promise<void> {
   const cards = await pb.collections.getOne("cards");
   const field = cards.fields.find(
@@ -1319,6 +1341,7 @@ async function main(): Promise<void> {
 
   // Add the project/prototype kind field for Phase 6.
   await ensureProjectKindField(pb);
+  await ensureProjectBackgroundMdField(pb);
 
   // Add the per-commit summary fields used by Phase 3b's AI one-liner job.
   await ensureCommitSummaryFields(pb);

src/lib/pb/types.ts

@@ -61,6 +61,8 @@ export interface ProjectRecord extends BaseRecord {
   session_gap_minutes: number;
   pre_session_minutes: number;
   post_session_minutes: number;
+  /** Developer's curated context for this app, sent into every wizard prompt. */
+  background_md: string;
 }
 
 export interface ColumnRecord extends BaseRecord {