Fix add_issue_comment schema compatibility regression

[SamMorrowDrums]

Summary

• remove top-level anyOf and dependentSchemas from add_issue_comment so its canonical input schema is a flat object accepted by stricter provider JSON Schema subsets
• keep body.minLength, the reaction enum, and comment_id integer/minimum constraints in the schema while retaining all cross-field validation in the handler
• add a non-mutating regression guard over the complete OSS tool inventory that rejects top-level anyOf, oneOf, or allOf

This is a patch-release fix for the v1.10.0 regression introduced by #3085. A single rejected schema breaks full-tool-list forwarding in headless Claude/CI clients before any tool can run. The fix is static and provider-portable: it does not mutate schemas or branch on negotiated MCP protocol versions.

Behavior compatibility

Input mode	Result
body only	Creates the issue/PR comment
reaction only	Reacts to the issue/PR
body + reaction	Preserves the existing combined behavior
comment_id + reaction	Reacts to the matching existing comment
Neither body nor reaction	Clear tool error
comment_id without reaction	Clear tool error
comment_id + body	Clear tool error
Empty body or reaction	Clear tool error
Zero, negative, fractional, or non-numeric comment_id	Clear tool error
Unsupported reaction	Clear tool error

Inventory and footprint

The emitted tools/list inventory contains 85 tools and has no top-level anyOf, oneOf, or allOf violations after this change. No other accidental instance required a fix.

The add_issue_comment toolsnap shrinks from 2,088 to 1,732 bytes (-356 bytes, -17.0%) and from 502 to 417 tokens with @anthropic-ai/tokenizer (-85 tokens, -16.9%).

A future runtime compatibility transform, if ever needed, should use an explicit client capability/profile and deep-clone or copy-on-write each inventory build; it should not mutate shared tool schemas or infer capabilities from the MCP protocol version.

Validation

• UPDATE_TOOLSNAPS=true go test ./...
• script/lint
• script/test
• script/generate-docs
• local stdio tools/list wire smoke over all toolsets (85 tools, zero top-level combinator violations)

Fixes#3126

[Copilot]

Pull request overview

Fixes provider compatibility by removing unsupported top-level schema combinators while preserving handler validation.

Changes:

• Flattens the add_issue_comment input schema.
• Expands schema and handler regression tests.
• Adds an inventory-wide combinator compatibility guard.

Show a summary per file

File	Description
pkg/github/issues.go	Removes incompatible schema constraints.
pkg/github/issues_test.go	Verifies schema and handler behavior.
pkg/github/tools_validation_test.go	Guards all tool schemas against top-level combinators.
pkg/github/__toolsnaps__/add_issue_comment.snap	Updates the schema snapshot.

Review details

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• Files reviewed: 4/4 changed files
• Comments generated: 0
• Review effort level: Balanced