[BUG] CLAUDE_APP_BOT_ID constant uses github-actions[bot] ID (41898282) instead of claude[bot] ID (209825114)

## Describe the bug

The `CLAUDE_APP_BOT_ID` constant in `src/github/constants.ts` is set to `41898282`, which is actually the ID for `github-actions[bot]`, not `claude[bot]`.

The correct ID for `claude[bot]` is `209825114`.

## Evidence

Verified via GitHub API:
```json
{"id": 41898282, "login": "github-actions[bot]", "type": "Bot"}
{"id": 209825114, "login": "claude[bot]", "type": "Bot"}
```

Looking at `action.yml`, the defaults are:
- `bot_id: "41898282"` ← WRONG (this is github-actions[bot])
- `bot_name: "claude[bot]"` ← Correct name, but mismatched with ID

## Impact

When commits are made via git CLI (fallback when API commit signing fails), the commits have:
- Author: `41898282+claude[bot]@users.noreply.github.com`
- This creates an identity mismatch and results in **unsigned commits**

Compare to correctly-signed commits made via GitHub API:
- Author: `209825114+claude[bot]@users.noreply.github.com`
- Committer: `GitHub `
- These are **verified/signed** by GitHub

## Reproduction

1. Enable `use_commit_signing: true` in a workflow
2. Trigger Claude to make a commit
3. In some cases, commits fall back to git CLI instead of API
4. These commits show as unsigned in GitHub

## Workaround

Explicitly set the correct `bot_id` in workflow:
```yaml
- uses: anthropics/claude-code-action@v1
with:
use_commit_signing: true
bot_id: "209825114" # ← Workaround: correct claude[bot] ID
```

## Suggested Fix

Update `src/github/constants.ts`:
```typescript
// Before (incorrect)
export const CLAUDE_APP_BOT_ID = 41898282;

// After (correct)
export const CLAUDE_APP_BOT_ID = 209825114;
```

And update the default in `action.yml`:
```yaml
bot_id:
description: "GitHub user ID to use for git operations"
required: false
default: "209825114" # claude[bot] ID
```

## Related

This may be related to #281 / #282 (commits not verified), though those issues focus on when git CLI is used rather than the incorrect bot ID.