refactor: remove uwf cas subcommand, use ocas CLI

- Remove entire 'uwf cas' command group from CLI
- Delete commands/cas.ts (only used by CLI + tests)
- Delete cas.test.ts and cas-exit-code.test.ts
- Update workflow YAMLs: uwf cas get/has/refs/walk → ocas
- Update e2e-walkthrough script to use ocas
- Update docs and reference files
- Keep store-global-cas.test.ts (internal CAS store tests)

CAS operations now go through 'ocas' CLI exclusively.
Agent text storage handled internally by uwf pipeline.

Closes #10

workflows/solve-issue.yaml

@@ -29,7 +29,7 @@ roles:
 
       After producing the test spec:
 
-      1. Store it via `uwf cas put-text "<markdown content>"` and capture the returned hash
+      1. The test spec is stored in CAS automatically by the uwf pipeline (agents do not need to call `ocas put` directly)
 
       2. Put the hash in frontmatter.plan (required when $status=ready)
 
@@ -79,7 +79,7 @@ roles:
       \ set up an isolated worktree:\n1. cd into the repo path provided in your task prompt\n2. `git fetch origin` to get latest refs\n3. First time (no existing branch):\n   - `git worktree add .worktrees/fix/<issue-number>-<short-slug>\
       \ -b fix/<issue-number>-<short-slug> origin/main`\n   - `cd .worktrees/fix/<issue-number>-<short-slug> && bun install`\n4. If bounced back from reviewer or tester (branch already exists):\n   - cd\
       \ into the existing worktree under `.worktrees/fix/<issue-number>-<short-slug>`\n   - `git fetch origin && git rebase origin/main`\n5. ALL subsequent work must happen inside the worktree directory.\n\
-      \nThen implement TDD:\n6. Read the test spec from CAS: `uwf cas get <plan hash>` (find the hash from the planner's output in your task prompt)\n7. If bounced back from reviewer or tester: read the\
+      \nThen implement TDD:\n6. Read the test spec from CAS: `ocas get <plan hash>` (find the hash from the planner's output in your task prompt)\n7. If bounced back from reviewer or tester: read the\
       \ previous role's feedback in your task prompt\n8. Write tests first based on the spec (use vitest)\n9. Implement the code to make tests pass\n10. Ensure `bun run build` passes with no errors\n11.\
       \ Run `bun test` to verify all tests pass\n\nIf you cannot complete the implementation (e.g. the issue is too complex, blocked by external factors,\nor repeated attempts fail), set $status=failed\
       \ with a reason.\n"
@@ -192,7 +192,7 @@ roles:
     goal: You are a tester agent. You verify that the implementation correctly satisfies every scenario in the test spec.
     capabilities:
     - testing
-    procedure: "The worktree path is provided in your task prompt. cd into it first.\n\n1. Run `bun test` for automated test verification\n2. Read the test spec from CAS: `uwf cas get <plan hash>` (find\
+    procedure: "The worktree path is provided in your task prompt. cd into it first.\n\n1. Run `bun test` for automated test verification\n2. Read the test spec from CAS: `ocas get <plan hash>` (find\
       \ the hash from the planner step in the thread history)\n3. Verify each scenario in the spec is covered and passing\n4. Determine outcome:\n   - passed: all scenarios verified, tests pass\n   - fix_code:\
       \ tests fail or implementation doesn't match spec → send back to developer\n   - fix_spec: the spec itself is wrong or incomplete → send back to planner\n"
     output: Report test results per scenario. Set $status to passed (with branch/worktree), fix_code (with report), or fix_spec (with report).