fix: unify mixed-format tool block handling across task + condense

[daniel-lxs]

Summary

• add shared tool block format helpers for legacy (tool_use/tool_result) and AI SDK (tool-call/tool-result) shapes
• refactor Task, condense, and validateToolResultIds to use shared helpers instead of duplicated local type guards/mappers
• preserve mixed-format behavior in resume, condense orphan filtering, synthetic tool result injection, and tool-result ID reconciliation
• add mixed-format regression tests for condense and tool-result validation

Why

Message history is currently a mix of legacy Anthropic and AI SDK shapes during migration. Prior logic handled these formats inconsistently across code paths, which risked orphan filtering mistakes and resume/protocol mismatches.

Testing

• pnpm --dir src exec tsc --noEmit --pretty false
• pnpm --dir src exec vitest run core/condense/__tests__/index.spec.ts core/task/__tests__/validateToolResultIds.spec.ts core/task/__tests__/Task.persistence.spec.ts core/task/__tests__/flushPendingToolResultsToHistory.spec.ts
• push hook suite (repo check-types + full tests) passed during git push

[roomote]

Rooviewer   See task

Re-reviewed after merge commit c1ab9ad. The merge with main adopted the rooMessage.ts dual-format helper approach from #11409, fully superseding this PR's toolBlockFormat.ts approach. The branch tree is now identical to main -- zero net changes. Previous format mismatch issue is resolved. No new issues.

• injectSyntheticToolResults always emits legacy tool_result format for AI SDK orphans, unlike validateToolResultIds which matches the format via prefersAiSdkToolResultFormat

Previous reviews

• 2161f60: Review #1

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