tool: trim persisted LSP diagnostics in edit/write metadata

[Schubox84]

What & why

On every edit/write, lsp.diagnostics() returns the whole workspace map (every file across every LSP client). That full map is persisted verbatim into the tool-result metadata, which the session stores and replays/prompts on future turns. For workspace-wide Lua/TS/etc. diagnostics this balloons the session transcript and hastens compaction.

This trims the persistedmetadata.diagnostics down to only the touched file, while keeping the full map in-memory for the per-call output computation (unchanged agent behavior).

Changes

• packages/opencode/src/tool/write.ts — persist { [normalizedFilepath]: issues } instead of the whole map.
• packages/opencode/src/tool/edit.ts — same trim (edit already only emits the touched file's diagnostics in output).
• packages/opencode/test/tool/lsp-diagnostics-metadata.test.ts — regression coverage: a fake LSP service returns a workspace-wide map and the tests assert persisted metadata contains only the touched file.

Why it's safe

• Diagnostics are recomputed per call via touchFile + diagnostics(); metadata is persistence/debug only and not used to derive the model-facing output.
• The output block (which the agent actually reads) is unchanged — it already separates "this file" vs "other files" and is capped by MAX_PROJECT_DIAGNOSTICS_FILES.
• Follows the intent of the earlier closed PR tool: trim persisted LSP diagnostics #6671, re-implemented against the current Effect-based LSP service.

Verification

• tsgo --noEmit clean
• bun test test/tool/lsp-diagnostics-metadata.test.ts — 2 pass
• Existing write/edit suites pass (one pre-existing umask-dependent file-permission test fails only under umask 0002, unrelated).

[github-actions]

Hey! Your PR title tool: trim persisted LSP diagnostics in edit/write metadata doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
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• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

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[github-actions]

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[Schubox84]

Ready for review. This is a re-implementation of the earlier closed PR #6671, updated to the current Effect-based LSP service — trims the persisted metadata to the touched file only; the model-facing output is unchanged.

[github-actions]

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