claude-code-action silently drops output comments on issue_comment triggers

## Description

When `claude-code-action` is triggered via `issue_comment` events, Claude runs successfully (consuming tokens, executing tools) but the action's built-in comment-posting mechanism frequently produces no visible GitHub comment. The post-execution step logs "No buffered inline comments" and no PR/issue comment is posted.

## Reproduction

1. Configure `claude-code-action` on an `issue_comment` trigger (both `auto-review` and `claude` agent modes)
2. Post a comment like `@claude can you code review this for me please?` on a PR
3. The workflow runs to completion (`success`), Claude uses ~350k input tokens and generates ~4800 output tokens
4. No comment is posted on the PR

## Observed behavior

- Workflow completes with `success` status
- Logs show `No buffered inline comments`
- No GitHub comment is posted
- This happens consistently on trivial diffs (auto-review mode) and on `@claude` mentions (agent mode)

## Expected behavior

Claude's response should always be posted as a GitHub comment, regardless of diff size or trigger type.

## Workaround

Instructing Claude in the prompt to explicitly use `gh issue comment` or `gh pr comment` for all responses works — when Claude posts comments via its own tool calls during execution, they appear correctly. The issue is specifically with the action's post-execution comment posting.

## Environment

- `anthropics/claude-code-action@v1`
- Trigger: `issue_comment` (created)
- Model: claude-sonnet-4-6 (action default)
- Example run: https://github.com/solo-ist/prose/actions/runs/23176274422

Reproduce the issue with an issue_comment trigger in both auto-review and claude modes, then trace the post-execution path that logs "No buffered inline comments." Compare the buffered-comment path with the working gh issue comment workaround. Done means Claude's response reliably appears as a GitHub comment for trivial diffs and @claude mentions.

Written by the indexing model from the issue text.