Gitea provider: list_all_commits fetches repo commits instead of PR commits

[hholst80]

Bug Description

The Gitea provider's __init__ method in pr_agent/git_providers/gitea_provider.py fetches all repository commits instead of PR-specific commits, causing self.last_commit to point at the wrong commit.

Root Cause

# gitea_provider.py, lines 89-93
self.pr_commits = self.repo_api.list_all_commits(
    owner=self.owner,
    repo=self.repo
)
self.last_commit = self.pr_commits[-1]

list_all_commits() calls GET /repos/{owner}/{repo}/commits, which returns commits from the default branch (e.g. master/main), not from the PR branch. Then [-1] picks the last element — which, since Gitea returns commits newest-first, is the oldest commit on the default branch.

Compare with the GitHub provider which correctly uses PR-specific commits:

# github_provider.py, line 53-54
self.pr_commits = list(self.pr.get_commits())
self.last_commit_id = self.pr_commits[-1]

Impact

• get_latest_commit_url() (line 226) returns the URL of a random default-branch commit, not the PR head.
• Persistent review updates always report "updated to latest commit {wrong_sha}" — referencing a commit that has nothing to do with the PR.
• publish_inline_comments() (line 317) posts inline comments against the wrong commit_id.
• _get_file_content_from_latest_commit() (line 439) fetches file content from the wrong commit.
• /review re-runs don't detect new changes — since last_commit SHA never changes (it's always the same default-branch commit), the persistent review thinks nothing changed and doesn't re-analyze.

Steps to Reproduce

1. Set up PR-Agent with a Gitea instance
2. Create a PR with one or more commits
3. Trigger /review — note the commit SHA in the persistent review header
4. Push a new commit to the PR branch
5. Trigger /review again — the persistent review still references the same wrong commit SHA from step 3, and the review content is not updated

Suggested Fix

Replace list_all_commits(owner, repo) with a method that calls the PR-specific commits endpoint:

GET /repos/{owner}/{repo}/pulls/{pr_number}/commits

The giteapy SDK (v1.0.8) does not have a built-in method for this endpoint, so a raw call_api call is needed (following the same pattern as get_change_file_pull_request and get_pull_request_diff).

Also note that Gitea returns PR commits newest-first (unlike GitHub which returns oldest-first), so [0] should be used instead of [-1] to get the latest commit.