Multiple jobs overwrite each other's PR comments

## Problem

When using `claude-code-action` in multiple parallel jobs within the same workflow (e.g., separate "Code Quality Review" and "Security Review" jobs), the PR comments overwrite each other. Only the last job's comment remains visible.

## Expected Behavior

Each job should be able to post its own independent comment that persists, allowing for:
- Separate code quality review comment
- Separate security review comment
- Any other specialized review comments

## Current Behavior

When two jobs run in parallel:
```yaml
jobs:
code-review:
steps:
- uses: anthropics/claude-code-action@v1
with:
prompt: "Review code quality..."

security-review:
steps:
- uses: anthropics/claude-code-action@v1
with:
prompt: "Review security..."
```

The second job's comment overwrites the first one, resulting in only one visible comment.

## Attempted Workarounds

1. **Using `use_sticky_comment: false`** - Comments still collide
2. **Using `marocchino/sticky-pull-request-comment`** with different `header` values - Doesn't work because `claude-code-action` posts its own comment regardless
3. **Combining prompts into single job** - Works but loses the benefit of parallel execution and separate concerns

## Proposed Solutions

1. Add a `comment_id` or `comment_header` parameter to differentiate comments from different jobs
2. Support for custom comment posting (disable built-in commenting, expose result as output only)
3. Built-in support for multiple review types with separate comments

## Environment

- Action version: v1
- Workflow trigger: pull_request

## Use Case

We want to run specialized reviews in parallel:
- Code quality review
- Security review (SQL injection, auth issues, etc.)

Each review has different prompts and should produce separate, persistent comments.