fix(core): isolate invalid plugin tools during materialize

[BrightonXX]

Issue for this PR

Closes #35963

Type of change

• Bug fix

What does this PR do?

A structurally invalid plugin tool (missing description, undecodable schema, opaque object from a different module copy) throws inside materialize() and breaks every subsequent model step in the Location because no definition list can be produced.

materialize() now wraps each definition() call in try/catch. On failure: log a warning with the tool name and error, drop the registration from the direct map so later settle() calls do not surface it as usable, and continue building the rest of the catalog. The dropped tool settles as Unknown tool: <name> instead of re-throwing.

How did you verify your code works?

cd packages/core && bun test test/session-runner-tool-registry.test.ts   # 18 pass, 0 fail
bun turbo typecheck --filter=@opencode-ai/core...                         # 17/17 green

Reverse verification: reverting packages/core/src/tool/registry.ts makes the new test fail with TypeError: Cannot read properties of undefined (reading '~context') from inside materialize().

Screenshots / recordings

Not applicable — this is a core logic change, not a UI change.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

[github-actions]

Thanks for your contribution!

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1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

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