refactor: unify env vars (UWF_HOME, OCAS_HOME) + env only in CLI (#37)

Breaking changes:
- UWF_STORAGE_ROOT → UWF_HOME
- WORKFLOW_STORAGE_ROOT removed (no fallback)
- OCAS_DIR → OCAS_HOME (aligned with ocas CLI)

Library functions no longer read process.env:
- util-agent/storage.ts: resolveStorageRoot(override), getGlobalCasDir(override)
- agent-hermes: isResumeDisabled(flag) pure function, CLI reads env
- agent-claude-code: CLI reads CLAUDE_MODEL and passes to agent

Fixes #37

packages/util/src/user-reference.ts

@@ -37,7 +37,7 @@ uwf setup --provider <name> --base-url <url> \\
            [--agent <name>]                         # optional default agent
 \`\`\`
 
-Config is stored at \`~/.uwf/config.yaml\`. Override storage root with \`UWF_STORAGE_ROOT\` (or \`WORKFLOW_STORAGE_ROOT\`).
+Config is stored at \`~/.uwf/config.yaml\`. Override storage root with \`UWF_HOME\`.
 
 ## Workflow Commands