fix: remove 10 more unnecessary as any casts in opencode core

[kitlangton]

Summary

Follow-up to #22877. Removes 10 more as any casts from packages/opencode/src/.

Changes

• session/prompt.ts — the id: ... as any inside tool({...}) was bogus. The id field on the AI SDK Tool type only exists for type: 'provider' tools (with a ${string}.${string} template literal format); for user-defined tools you register them under an id key on the outer tools object, not inside the tool itself. Dropping those fields removes 2 casts. The inputSchema: jsonSchema(... as any) casts were unnecessary: the ProviderTransform.schema(...) call already returns JSONSchema7 (removing 1 cast), and the other site now imports JSONSchema7 from @ai-sdk/provider instead of widening to any.
• server/instance/experimental.ts — replace zodToJsonSchema (from zod-to-json-schema, which expects the zod v3 ZodSchema<any>) with z.toJSONSchema from the existing zod v4 import. This kills the (t.parameters as any)?._def ? zodToJsonSchema(t.parameters as any) : t.parameters dead fallback — every Tool.Def.parameters is a z.ZodType by construction, so the "is this a Zod schema?" branch was unreachable.
• config/config.ts — inline { config?: Record<string, unknown> } for the .well-known/opencode JSON response.
• lsp/server.ts — inline { assets?: { name?: string; browser_download_url?: string }[] } for the GitHub releases response (matching the existing shape used further down in the same file at line 1580). Tightens the release.assets.find((a: any) => ...) callback to drop its own a: any and adds a browser_download_url presence check before use.
• cli/cmd/tui/routes/session/index.tsx:
  • WebFetch — remove 2 casts by accessing props.input.url directly (ToolProps<typeof WebFetchTool> already gives us the shape).
  • CodeSearch / WebSearch — change ToolProps<any> to ToolProps<typeof CodeSearchTool> / ToolProps<typeof WebSearchTool> so props.input.query is typed. The metadata casts are retained but narrowed from any to { results?: number } / { numResults?: number } (true type would require touching the tool metadata schemas — deferred).
  • Task — narrow x.state.title access via the status === "running" || status === "completed" discriminant (Pending/Error states don't have title).

Remaining

~15 as any casts still in packages/opencode/src/, all at genuine type boundaries or dynamic dispatch sites:

• plugin/plugin.ts (3) — dynamic hook dispatch (internal bus payload ↔ SDK Event, plugin config type mismatch)
• lsp/client.ts (2) — Node child process stream ↔ vscode-languageserver-protocol stream
• util/filesystem.ts (1) — DOM ↔ Node ReadableStream bridge
• util/effect-zod.ts (1) — symbol key on interface with only string index signature
• provider/provider.ts (1) — internal Auth.Info ↔ plugin SDK Auth
• tool/registry.ts (1) — plugin args boundary (runtime-validated unknown ↔ user-defined Zod shape)
• cli/cmd/tui/routes/session/index.tsx (1) — SolidJS <Dynamic> component/props inference

Verification

• bun turbo typecheck passes (all 13 tasks).
• bun run lint passes (oxlint warnings only, no errors).
• bun test test/session/structured-output-integration.test.ts passes (checks the createStructuredOutputTool path).