Replace bugsy with libmozdata for Bugzilla MCP in Hackbot

[suhaibmujahid]

Resolves #6179

[Copilot]

Pull request overview

This PR updates Hackbot’s Bugzilla MCP broker and agent tool implementations to use libmozdata instead of bugsy, aligning with the project’s existing dependency stack and resolving #6179.

Changes:

• Switched Bugzilla tool implementation (agent_tools.bugzilla) from bugsy to libmozdata and updated the broker to construct a URL/key context instead of a bugsy client.
• Updated dependency declarations/lockfile entries to drop bugsy and add libmozdata~=0.2.12 for the bugzilla extra.
• Reworked/expanded Bugzilla tool tests to mock libmozdata’s handler-based API flow and cover additional read tools (comments/attachments/download).

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
uv.lock	Removes bugsy from the Bugzilla extra metadata and adds libmozdata pinning for the extra.
libs/agent-tools/tests/test_bugzilla.py	Updates tests to patch Bugzilla with a handler-replay fake and adds broader tool coverage.
libs/agent-tools/pyproject.toml	Replaces the bugzilla extra dependency from bugsy to libmozdata~=0.2.12.
libs/agent-tools/agent_tools/bugzilla.py	Re-implements Bugzilla read-only tools using libmozdata + structured error mapping from requests.HTTPError.
agents/bug-fix/pyproject.toml	Drops direct bugsy dependency (now satisfied via agent-tools[bugzilla]).
agents/bug-fix/hackbot_agents/bug_fix/broker.py	Updates broker startup to use BugzillaContext(api_url, api_key) instead of constructing a bugsy client.

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