docs: clarify agent mode only works with workflow_dispatch and schedule events (#378)

* docs: clarify agent mode only works with workflow_dispatch and schedule events

Updates documentation to match the current implementation where agent mode
is restricted to workflow_dispatch and schedule events only. This addresses
the confusion reported in issues #364 and #376.

Changes:
- Updated README to clearly state agent mode limitations
- Added explicit note that agent mode does NOT work with PR/issue events
- Updated example workflows to only show supported event types
- Updated CLAUDE.md internal documentation

Fixes #364
Fixes #376

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* minor formatting update

* update agent mode docs

---------

Co-authored-by: km-anthropic <km-anthropic@users.noreply.github.com>
Co-authored-by: Claude <noreply@anthropic.com>

CLAUDE.md

@@ -53,7 +53,7 @@ Execution steps:
 #### Mode System (`src/modes/`)
 
 - **Tag Mode** (`tag/`): Responds to `@claude` mentions and issue assignments
-- **Agent Mode** (`agent/`): Automated execution without trigger checking
+- **Agent Mode** (`agent/`): Automated execution for workflow_dispatch and schedule events only
 - Extensible registry pattern in `modes/registry.ts`
 
 #### GitHub Integration (`src/github/`)
@@ -118,7 +118,7 @@ src/
 
 - Modes implement `Mode` interface with `shouldTrigger()` and `prepare()` methods
 - Registry validates mode compatibility with GitHub event types
-- Agent mode bypasses all trigger checking for automation scenarios
+- Agent mode only works with workflow_dispatch and schedule events
 
 ### Comment Threading