feat: add Claude Code agent for Anthropic model users (#502)

* feat: add Claude Code agent for Anthropic model users

Re-adds Claude Code support (removed in #478) so users with Anthropic API
keys or Claude Code OAuth tokens can use their Claude subscriptions directly.

When an Anthropic model is selected and Claude Code credentials are available,
the system auto-selects the Claude agent instead of OpenCode. The harness
mirrors opentoad's security model: native Bash blocked via --disallowedTools,
MCP ShellTool for restricted shell, ASKPASS for git auth. Includes NDJSON
streaming, provider error detection, cache/cost tracking, browser skill,
and todo progress tracking.

Key changes:
- action/agents/claude.ts: full Claude Code harness
- action/utils/agent.ts: auto-select Claude for anthropic/* models
- action/utils/providerErrors.ts: extracted shared provider error detection
- action/utils/skills.ts: extracted shared skill installation (agent-aware)
- action/models.ts: add CLAUDE_CODE_OAUTH_TOKEN to anthropic envVars
- action/utils/docker.ts: add CLAUDE_CODE_OAUTH_TOKEN to test env allowlist
- CI: add claude to test matrix, pass CLAUDE_CODE_OAUTH_TOKEN secret

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: remove unused toolId variable, fix apiKeys test env cleanup

The apiKeys test cleanup stripped *_API_KEY vars but missed
CLAUDE_CODE_OAUTH_TOKEN which doesn't match that pattern.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* fix: strip provider prefix from PULLFROG_MODEL in Claude agent

the env override path was returning the raw value (e.g.
"anthropic/claude-sonnet-4-5") without stripping the provider prefix,
causing the Claude CLI to receive an invalid model ID.

Made-with: Cursor

* fix: remove dead cliPath field, add CLAUDE_CODE_OAUTH_TOKEN to workflows

remove unused cliPath from Claude agent RunParams, and pass
CLAUDE_CODE_OAUTH_TOKEN through all pullfrog.yml workflow templates
so users with Claude Pro/Team subscriptions can use their membership.

Made-with: Cursor

* fix: block Bash subagent in Claude Code disallowedTools

Made-with: Cursor

* chore: update model snapshot (opencode/openrouter latest → qwen3.6-plus-free)

Made-with: Cursor

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

main.ts

@@ -237,7 +237,7 @@ export async function main(): Promise<MainResult> {
     await using gitAuthServer = await startGitAuthServer(tmpdir);
     setGitAuthServer(gitAuthServer);
 
-    const agent = resolveAgent();
+    const agent = resolveAgent({ model: payload.proxyModel ? undefined : payload.model });
 
     validateAgentApiKey({
       agent,