refactor: wave 1 - extract leaf modules, rename catch-all files, split index.ts hooks

- Split 25+ index.ts files into hook.ts + extracted modules
- Rename all catch-all utils.ts/helpers.ts to domain-specific names
- Split src/tools/lsp/ into ~15 focused modules
- Split src/tools/delegate-task/ into ~18 focused modules
- Separate shared types from implementation
- 155 files changed, 60+ new files created
- All typecheck clean, 61 tests pass

src/tools/lsp/diagnostics-tool.ts

@@ -0,0 +1,53 @@
+import { tool, type ToolDefinition } from "@opencode-ai/plugin/tool"
+
+import { DEFAULT_MAX_DIAGNOSTICS } from "./constants"
+import { filterDiagnosticsBySeverity, formatDiagnostic } from "./lsp-formatters"
+import { withLspClient } from "./lsp-client-wrapper"
+import type { Diagnostic } from "./types"
+
+export const lsp_diagnostics: ToolDefinition = tool({
+  description: "Get errors, warnings, hints from language server BEFORE running build.",
+  args: {
+    filePath: tool.schema.string(),
+    severity: tool.schema
+      .enum(["error", "warning", "information", "hint", "all"])
+      .optional()
+      .describe("Filter by severity level"),
+  },
+  execute: async (args, context) => {
+    try {
+      const result = await withLspClient(args.filePath, async (client) => {
+        return (await client.diagnostics(args.filePath)) as { items?: Diagnostic[] } | Diagnostic[] | null
+      })
+
+      let diagnostics: Diagnostic[] = []
+      if (result) {
+        if (Array.isArray(result)) {
+          diagnostics = result
+        } else if (result.items) {
+          diagnostics = result.items
+        }
+      }
+
+      diagnostics = filterDiagnosticsBySeverity(diagnostics, args.severity)
+
+      if (diagnostics.length === 0) {
+        const output = "No diagnostics found"
+        return output
+      }
+
+      const total = diagnostics.length
+      const truncated = total > DEFAULT_MAX_DIAGNOSTICS
+      const limited = truncated ? diagnostics.slice(0, DEFAULT_MAX_DIAGNOSTICS) : diagnostics
+      const lines = limited.map(formatDiagnostic)
+      if (truncated) {
+        lines.unshift(`Found ${total} diagnostics (showing first ${DEFAULT_MAX_DIAGNOSTICS}):`)
+      }
+      const output = lines.join("\n")
+      return output
+    } catch (e) {
+      const output = `Error: ${e instanceof Error ? e.message : String(e)}`
+      throw new Error(output)
+    }
+  },
+})