fix(providers): strip $schema recursively and downgrade fallback log level

[penso]

Summary

Fixes #760 — schema normalization WARN logs repeated 1000+ times per session.

• Recursive $schema stripping: json_schema_ast validates $schema at every nesting level, so root-only stripping was insufficient for schemas with $schema inside nested definitions/$defs (e.g. Attio MCP tools). Now strips recursively before canonicalization.
• Downgraded log level: The fallback path works correctly — logging at warn! was inappropriate for an expected state. Changed to debug! per project logging conventions.

Validation

Completed

• cargo +nightly-2025-11-30 fmt --all -- --check
• just lint (clippy clean)
• just test (367 tests pass)
• New test: sanitize_draft07_nested_definitions_schema_canonicalized — verifies schemas with $schema in nested definitions go through full canonicalization (not fallback)
• New test: sanitize_draft07_schema_uses_canonicalization_not_fallback — verifies root-level draft-07 schemas also trigger canonicalization
• Both tests detect the issue before the fix (verified by reverting and re-running)

Manual QA

1. Run moltis serve with an OpenAI-compatible provider (e.g. OpenRouter)
2. Connect MCP tools that use draft-07 schemas (e.g. Attio)
3. Start a chat session and trigger tool calls
4. Check ~/.config/moltis/logs.jsonl — no more WARN spam from schema_normalization
5. Verify tools still function correctly (schemas are normalized via canonicalization, not fallback)

🤖 Generated with Claude Code

[greptile-apps]

Greptile Summary

Fixes repeated WARN-level log spam (#760) caused by $schema keywords embedded inside nested definitions/$defs blocks of MCP tool schemas (e.g. Attio). The previous root-only strip left nested $schema URIs intact, causing json_schema_ast to reject the schema at inner pointers and fall through to the best-effort path on every tool call. The recursive stripping function resolves the root cause, and the log-level downgrade to debug! is consistent with project conventions for expected-recoverable states.

Confidence Score: 5/5

Safe to merge — targeted fix with no correctness risk and two regression tests that verify the non-fallback code path.

No P0/P1 findings. The recursive stripping is correct (handles objects and arrays, removes $schema before recursing into sibling values). The debug! downgrade matches CLAUDE.md conventions for expected-recoverable states. Both new tests are well-designed: they detect the fallback path indirectly via the lower_boolean_and_null_types canonicalization side-effect, and the PR description confirms they failed before the fix.

No files require special attention.

Important Files Changed

Filename	Overview
crates/providers/src/openai_compat/schema_normalization.rs	Adds recursive $schema stripping via strip_schema_keyword_recursive and downgrades three fallback log levels from warn! to debug! — both changes are correct and align with project conventions.
crates/providers/src/openai_compat/tests.rs	Adds two well-designed regression tests that verify canonicalization runs (not the fallback path) by asserting the lower_boolean_and_null_types side-effect (enum: [false, true]) is present after sanitization.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A["sanitize_schema_for_openai_compat(schema)"] --> B["canonicalize_schema_for_openai_compat(schema)"]
    B --> C["schema.clone() → input"]
    C --> D["strip_schema_keyword_recursive(&mut input)\n(NEW: recurses into objects + arrays)"]
    D --> E["SchemaDocument::from_json(&input)"]
    E -->|Err| F["debug! preflight failed\nreturn input as-is"]
    E -->|Ok| G["document.root()"]
    G -->|Err| H["debug! AST resolution failed\nreturn input as-is"]
    G -->|Ok| I["document.canonical_schema_json()"]
    I -->|Err| J["debug! canonicalization unavailable\nreturn input as-is"]
    I -->|Ok| K["canonical serde_json::Value"]
    K --> L["Schema::try_from(canonical)"]
    L --> M["Apply schemars transforms\nReplaceConst / ReplaceUnevaluatedProperties\nReplacePrefixItems / RemoveRefSiblings\nOpenAiSchemaSubset / SimplifyComposite\nPruneOrphanedRequired / RestoreEnumType"]
    M --> N["*schema = transformed.to_value()"]

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[codecov]

Codecov Report

❌ Patch coverage is 88.23529% with 2 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...roviders/src/openai_compat/schema_normalization.rs	88.23%	2 Missing ⚠️

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[codspeed-hq]

Merging this PR will not alter performance

✅ 39 untouched benchmarks
⏩ 5 skipped benchmarks¹

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_{Comparing tough-net (77abc54) with main (c733c91)}

Footnotes

1. 5 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩