Fix TRY003: extract exception messages to variables and remove suppression

[Copilot]

Ruff rule TRY003 ("Avoid specifying long messages outside the exception class") was globally suppressed. This removes that suppression by fixing all ~48 violations across the codebase.

Approach

Each violation is fixed by extracting the message string into a local msg variable before the raise:

# Before
raise ValueError(f"No such reusable taskflow: {task.uses}")

# After
msg = f"No such reusable taskflow: {task.uses}"
raise ValueError(msg)

This satisfies TRY003 without requiring new exception subclasses or altering error messages.

Changes

• Source files (agent.py, available_tools.py, capi.py, cli.py, mcp_lifecycle.py, mcp_servers/codeql/client.py, mcp_servers/codeql/mcp_server.py, mcp_transport.py, mcp_utils.py, models.py, runner.py, session.py, shell_utils.py, template_utils.py): extract exception messages to msg variables
• mcp_servers/codeql/client.py: also fixes a pre-existing bug where an f-string was missing its f prefix ("Unsupported output format {fmt}" → f"Unsupported output format {fmt}")
• pyproject.toml: removes TRY003 from the global ignore list; adds a per-file ignore for the vendored third-party jsonrpyc package

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• unsupported.example.com
  • Triggering command: /usr/bin/python python -m pytest tests/ -x -q (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)