ci: run the db project as its own workspaces-c lane

workspaces-b became the slowest PR check (499-593s) once the server shards
were rebalanced. The @paperclipai/db project alone was 168-250s of its
436-513s of vitest time (PR runs 38084171761, 38083084276 and 38083020834,
2026-10-10). Vitest's native --shard would not level it: the project is
already file-parallel and client.test.ts is 117-189s of its wall time, so
a hash-ordered slice can put both slow suites on one runner.

The db project now runs as general-workspaces-c in both pr-trusted.yml and
release-verify.yml; workspaces-b keeps the other sixteen projects at
~265-275s of vitest time. Local `all` mode still covers every project, and
the guard tests assert that the three workspace lanes cover the root Vitest
project list exactly once and that both workflows carry the new lane.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

.github/workflows/pr-trusted.yml

@@ -585,8 +585,16 @@ jobs:
             group_label: workspaces-a (2/2)
             shard_index: 1
             shard_count: 2
+          # workspaces-b became the slowest check (499-593s) once the server
+          # shards were rebalanced: the db project alone was 168-250s of its
+          # 436-513s of vitest time (PR runs 38084171761, 38083084276 and
+          # 38083020834, 2026-10-10). The db project now runs as its own
+          # workspaces-c lane; the rest of workspaces-b is ~265-275s of
+          # vitest time, so both jobs land near 300-350s with setup.
           - group: general-workspaces-b
             group_label: workspaces-b
+          - group: general-workspaces-c
+            group_label: workspaces-c
 
     steps:
       - name: Checkout repository

.github/workflows/release-verify.yml

@@ -174,6 +174,9 @@ jobs:
             shard_count: 2
           - group: general-workspaces-b
             group_label: workspaces-b
+          # Keep parity with pr.yml: the db project runs as its own lane.
+          - group: general-workspaces-c
+            group_label: workspaces-c
 
     steps:
       - name: Checkout repository