fix(mcp): don't trip circuit breaker on tool errors

[renga-mn-agent]

What does this PR do?

Treats completed MCP CallToolResult(isError=True) responses as tool/domain errors rather than server connectivity failures.

A completed RPC proves the MCP transport is reachable. Counting a tool-level validation error toward the server circuit breaker can incorrectly mark a healthy MCP server as unreachable and prevent subsequent valid calls.

Related Issue

N/A

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

• Reset the server connectivity breaker after any completed tools/call RPC, including isError=True results.
• Preserve completed tool/domain errors returned after OAuth recovery or session reconnect instead of reclassifying them as auth/transport failures.
• Continue counting raised timeout, transport, and session failures toward the connectivity breaker.
• Add regression coverage for normal calls, OAuth retries, and session-reconnect retries.

How to Test

1. Run .venv/bin/python -m pytest tests/tools/test_mcp*.py -q -o 'addopts='.
2. Confirm repeated CallToolResult(isError=True) responses do not open the server connectivity breaker.
3. Confirm OAuth and session reconnect retries return completed tool errors unchanged.

Focused result: 385 passed.

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes (required for bug fixes, strongly encouraged for features)
• I've tested on my platform: Linux

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — docstrings updated
• I've updated cli-config.yaml.example if I added/changed config keys — N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — N/A
• I've considered cross-platform impact (Windows, macOS) per the compatibility guide — no platform-specific APIs added
• I've updated tool descriptions/schemas if I changed tool behavior — N/A

Screenshots / Logs

N/A

[renga-mn-agent]

Closing this PR to recreate it from the intended contributor account.

[renga-mn-agent]

Replacement: #74795, authored by @renga-kogahara.