Workspace concurrency review iteration: Jobs's 3 taste asks

Closes the three specific_asks from Jobs's T1 review of the workspace
architecture fix (7829acc..15e3863):

1. docs/architecture/workspace-concurrency.md: decision table
   upgraded from a code block to a real Markdown table so it reads
   consistently with the failure-modes table lower in the file.

2. docs/architecture/workspace-concurrency.md + resolve-workspace.ts:
   added "Sunset coding-role inference" section and a TODO marker on
   CODING_ROLE_PATTERN tying the regex to the v52 transition window
   (target 2026-05-20). Both documents now name the end-state
   explicitly so a future engineer knows why the regex exists and
   when it dies.

3. resolve-workspace.ts: enriched the WorkspaceConfigurationError
   message to include taskId / agentId / projectId alongside the
   existing companyId, so a misconfigured setup points operators at
   the offending row instead of just the company.

No behaviour change, no fallback, no mock. typecheck green, 540 unit
tests green, 10 eval tests green.

docs/architecture/workspace-concurrency.md

@@ -64,15 +64,24 @@ takes an exclusive lock on its agent workspace. Once every task
 creation path sets `requires_filesystem` explicitly the role inference
 becomes a no-op.
 
+### Sunset coding-role inference
+
+The coding-role regex in `resolve-workspace.ts` exists only for the
+v52 transition window. Before the next major, audit every
+`db.tasks.saveTask` caller, every migration seed, and any workflow
+that writes the `tasks` row; each must set `requires_filesystem`
+explicitly based on the task's real filesystem intent. When the audit
+is complete, delete the regex and the `agentSignalsFilesystem` branch
+from `inferLockMode` and remove this section. Target window: post
+v52 stabilisation, 2026-05-20.
+
 ## Decision table
 
-```
-task.workspaceId set          → exclusive on task.workspaceId
-task.requiresFilesystem=1     → exclusive on agent.workspaceId
-  OR agent role is coding       or project primary; throws if
-                                 neither exists
-everything else               → none / workspace=null
-```
+| Signal on the (task, agent) pair | Lock mode | Workspace used |
+| --- | --- | --- |
+| `task.workspaceId` set (explicit opt-in, e.g. PR-review task) | `exclusive` | The task's workspace |
+| `task.requiresFilesystem = 1` **OR** agent role matches coding pattern **OR** `agent.department = "engineering"` | `exclusive` | `agent.workspaceId` → project primary → throws `WorkspaceConfigurationError` |
+| Everything else (strategy, ops, finance, PM, drafting) | `none` | `null` — no lock claimed |
 
 Explicit `task.workspaceId` always wins. This is the escape hatch for
 "run this PR-review task on *that specific* branch workspace", and