docs(prd): PRD draft 0.3; slice 1 addendum A; lead decision 49

Darkwing's addendum as a record. Broker verbs enforce field ownership,
broker push from a bare repo, polling without webhooks, Vikunja probes
before the adapter interface is fixed.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/prd/mosaic-stack.md

@@ -1,13 +1,13 @@
 # PRD: Mosaic Stack
 
-- Status: draft, version 0.2. Jason approves it, and once approved it is
+- Status: draft, version 0.3. Jason approves it, and once approved it is
   never edited in place. Changes after approval are a new version.
 - Owner: Jason. Sage writes it from the PRDY interview.
 - Template: PRDY "software" (`v1/packages/prdy/src/templates.ts`), filled
   by hand until PRDY is ported.
 - Interview record: Sage's thread 1ef1e4f8. Round 1 is lead decision 45.
   Round 2 is lead decision 48. Design inputs are lead decisions 43, 44,
-  46 and 47.
+  46, 47 and 49.
 
 ## Introduction
 
@@ -111,9 +111,10 @@ parent requirement is refused.
     allowed in.
 - **REQ-VAR-2.** `~/.config/mosaic-dev/config.json` stays the only system
   config, and nothing writes it automatically. A secret appears only as a
-  reference, either a file path or an environment variable name. The
-  stack checks a referenced file with `stat` and never reads its
-  contents.
+  reference, either a file path or an environment variable name. Only
+  the broker reads a secret's contents. It holds them in memory and
+  never logs or writes them. Everything else checks a referenced file
+  with `stat`.
 
 ### Credentials
 
@@ -153,11 +154,13 @@ parent requirement is refused.
 ### Tasks
 
 - **REQ-TASK-1.** Tasks live in Vikunja, reached through `/api/v2` with a
-  bot token for each role. Each task cites a requirement id. Only the
-  assigned role writes a task's mutable fields. A person's edits come in
-  as events.
+  bot token for each role. Each task cites a requirement id. Each task
+  field has one writing role, listed in the slice 1 brief's field table,
+  and the assigned role writes the task's state. Vikunja's token scopes
+  cover whole route groups, so the broker's verbs enforce this, not the
+  tokens. A person's edits come in as events.
 - **REQ-TASK-2.** Polling for changes since the last check is the source
-  of truth, and webhooks only trigger a check sooner.
+  of truth, with an hourly full reconcile. Slice 1 uses no webhooks.
 - **REQ-TASK-3.** The installer offers two choices: point at an existing
   Vikunja, or deploy the bundled one. The bundled one is the unmodified
   upstream image. No Vikunja code enters the repository.