fix(cli): clear stale no_mcp and normalize numeric toolset names on save (#13028)

[dingn42]

Problem

_save_platform_tools() has two separate save-path defects (both reproducible by running the Python snippets in the issue body):

1. When a platform previously had the no_mcp disable-all sentinel and the user re-enables an MCP server, the sentinel survives the preserve-filter and silently re-suppresses the newly selected server on the next read. Observed: _get_platform_tools returned ['web'] immediately after saving {'web', 'exa'}.
2. YAML may parse bare numeric toolset names (e.g. 12306:) as int. The read path in _get_platform_tools already normalizes to str (lines 522-524), but the save path sorted mixed str/int entries and crashed with TypeError: '<' not supported between instances of 'str' and 'int'.

Fixes #13028.

Fix

• Normalize existing_toolsets to strings up front so sorted() on the merged set stays monomorphic — mirrors what _get_platform_tools already does on the read side.
• When enabled_toolset_keys contains any MCP server name (resolved from config['mcp_servers']), drop the no_mcp sentinel from preserved_entries. Plain saves that don't touch MCP still keep the sentinel.

Test plan

• Added two regression tests in tests/hermes_cli/test_tools_config.py:
  • test_save_platform_tools_clears_stale_no_mcp_when_enabling_mcp_server
  • test_save_platform_tools_normalises_numeric_existing_entries
• pytest tests/hermes_cli/test_tools_config.py — 34 passed
• Reran both Python reproducers from the issue against the fixed branch — first case: ['exa', 'web'] saved, ['exa', 'web'] enabled after reload; second case: no TypeError, 12306 round-trips as string

[teknium1]

Thanks for the thorough write-up and repro steps, @dingn42! Both fixes landed on main in a parallel commit before this PR could be merged.

Automated hermes-sweeper review found the following evidence:

• hermes_cli/tools_config.py line 802: existing_toolsets = [str(ts) for ts in existing_toolsets] — numeric normalization fix is present
• hermes_cli/tools_config.py line 814: preserved_entries.discard("no_mcp") — stale sentinel fix is present
• Implementing commit: 9d7b64b5dd394a60df7d38824256e2f213eac5c6 (fix(tools): normalize numeric entries and clear stale no_mcp in _save_platform_tools, merged 2026-04-24)
• Regression tests for both cases added to tests/hermes_cli/test_tools_config.py (lines 606 and 624)

The main implementation uses unconditional no_mcp discard on any hermes tools save (slightly broader than the MCP-server-name-conditional approach in this PR), but the outcome is the same for all the cases described in #13028. Closing as implemented. Your diagnosis and tests were valuable — the parallel fix picked up the same approach!