fix(gemini): stringify integer enum values in tool schemas

[BSubot]

Summary

Gemini's Schema.enum field strictly requires TYPE_STRING values. When a Hermes tool declares an integer enum (e.g. discord_server's auto_archive_duration=[60, 1440, 4320, 10080]), Gemini rejects the entire request with HTTP 400:

INVALID_ARGUMENT: Invalid value at 'tools[0].function_declarations[N].parameters.properties[M].value.enum[0]' (TYPE_STRING), 60

This happens even when the schema's type is integer — Gemini doesn't coerce. Any subagent routed to a Gemini model with the discord toolset (or any other tool containing integer enums) fails every API call, spamming gateway logs with non-retryable 400s.

Fix

In agent/gemini_schema.sanitize_gemini_schema, coerce every enum value to its str() representation before passing through. Lossless for downstream consumers — Gemini echoes back the string form and the tool dispatcher's JSON argument parsing already coerces integers.

Reproduction (before this PR)

>>> from agent.gemini_schema import sanitize_gemini_schema
>>> sanitize_gemini_schema({"type": "integer", "enum": [60, 1440]})
{'type': 'integer', 'enum': [60, 1440]}   # Gemini rejects this

After:

>>> sanitize_gemini_schema({"type": "integer", "enum": [60, 1440]})
{'type': 'integer', 'enum': ['60', '1440']}   # Gemini accepts

Tests

• Added tests/agent/test_gemini_schema.py with 6 cases: integer-enum stringification, string-enum preservation, mixed-type enum, nested enum inside properties, enum inside items, and non-list enum dropped.
• All 95 existing gemini adapter tests (test_gemini_native_adapter.py, test_gemini_cloudcode.py) still pass.

$ pytest tests/agent/test_gemini_schema.py tests/agent/test_gemini_native_adapter.py tests/agent/test_gemini_cloudcode.py -q
101 passed in 1.73s

Notes

• Only the enum path in sanitize_gemini_schema is touched; behaviour for every other schema key is unchanged.
• The only in-tree tool affected today is discord_server (tools/discord_tool.py), but the fix is tool-agnostic.

[alt-glitch]

Likely duplicate of #13486 — same root cause: integer enum in tool schema breaks Gemini. This PR fixes it in sanitize_gemini_schema rather than in the tool definition.

[alt-glitch]

Duplicate of #13486.

[andersmmg]

This seems like a better solution than the others, since it can cover other cases if they arise or are discovered, rather than requiring changes to the tools themselves