Add agent tools to read revisions from Phabricator

[suhaibmujahid]

Resolves #6433

[Copilot]

Pull request overview

This PR adds a read-only Phabricator (Differential) MCP tool surface and wires it into the bug-fix agent’s broker so follow-up runs triggered by Phabricator comments can fetch revision metadata, the full comment thread (including inline anchors), and the reviewed diff content.

Changes:

• Add new phabricator read-only tools: get_revision, get_revision_comments, get_revision_diff, including diff-size truncation and inline comment positioning.
• Extend the shared phabricator-client with revision lookup by ID and batched user PHID → username resolution.
• Update the bug-fix broker to mount separate Bugzilla and Phabricator MCP endpoints and pass the Phabricator MCP server config into follow-up runs.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
libs/phabricator-client/phabricator_client/client.py	Adds revision lookup by numeric id and user PHID resolution helper.
libs/phabricator-client/tests/test_client.py	Adds test coverage for the new client methods.
libs/agent-tools/agent_tools/phabricator.py	Introduces read-only Phabricator MCP tools and supporting parsing/helpers.
libs/agent-tools/tests/test_phabricator.py	Adds comprehensive tests for the new Phabricator tools.
agents/bug-fix/hackbot_agents/bug_fix/broker.py	Mounts /bugzilla/mcp and /phabricator/mcp plus reworks patch endpoint creation.
agents/bug-fix/hackbot_agents/bug_fix/config.py	Defines the Phabricator read-only MCP tool allowlist for follow-up runs.
agents/bug-fix/hackbot_agents/bug_fix/agent.py	Plumbs an optional Phabricator MCP server into the agent and investigator toolsets.
agents/bug-fix/hackbot_agents/bug_fix/main.py	Derives the Phabricator MCP URL from the broker URL for follow-up runs.
agents/bug-fix/hackbot_agents/bug_fix/prompts/follow-up.md	Instructs follow-up runs to read full Phabricator context before acting.
agents/bug-fix/tests/test_inputs.py	Tests derivation of the Phabricator MCP endpoint URL.
agents/bug-fix/tests/test_broker.py	Updates broker tests for new mounts and refactored patch route wiring.
agents/bug-fix/compose.yml	Updates Bugzilla MCP URL to the new /bugzilla/mcp mount.

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[evgenyrp]

I think at this point we should maintain concise, easily human-readable documentation on Hackbot and available functionality in /docs. When a change is made, this doc should also be changed. It can help with code reviews, understanding the state of the system, and obviously onboarding. It can even be sort of a changelog of what's happening.

[marco-c]

Approving on behalf of Evgeny since he already approved before, so we can merge.