Fix TRY003: encapsulate exception messages in custom exception classes

[Copilot]

TRY003 flags long exception messages constructed at the raise site rather than inside the exception class. This removes the suppression and fixes all 58 violations across the codebase.

Approach

Each unique error message is moved into a dedicated exception class __init__, so call sites pass typed context instead of formatted strings:

# Before
raise ValueError(f"model_settings in task {task.name or ''} needs to be a dictionary")

# After
class TaskModelSettingsTypeError(ValueError):
    def __init__(self, task_name: str) -> None:
        super().__init__(f"model_settings in task {task_name} needs to be a dictionary")

raise TaskModelSettingsTypeError(task.name or '')

New files

• exceptions.py — 25+ custom exception classes for the main package, organized by domain (API/token, MCP transport, runner, session, shell, template)
• mcp_servers/codeql/exceptions.py — CodeQL-specific exceptions (NoActiveDatabaseError, LegacyServerNotSupportedError, UnsupportedOutputFormatError, etc.)

Updated files

• available_tools.py — adds BadToolNameError/FileTypeException subclasses (InvalidToolFormatError, ToolDirNotFoundError, FiletypeMismatchError, etc.) so existing except BadToolNameError handlers are unaffected
• All other affected modules import and use the new exception types

pyproject.toml

• Removes TRY003 from the global ignore list
• Adds per-file-ignores for the vendored jsonrpyc/__init__.py to preserve that third-party code unchanged

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/ -v (dns block)
  • Triggering command: /usr/bin/python python -m pytest tests/ -q get --global git committer.email (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)