refactor: consolidate TUI harness into src/tui-harness/

Move harness code from two separate directories (src/test-utils/tui-harness/
and src/mcp-harness/) into a single src/tui-harness/ directory with lib/ and
mcp/ subdirectories. Also cleans up dead code in tools.ts, derives SpecialKey
type from SPECIAL_KEY_VALUES array (single source of truth), and fixes
cross-boundary import of createMinimalProjectDir.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: aidandaly24

esbuild.config.mjs

@@ -63,7 +63,7 @@ console.log('CLI build complete: dist/cli/index.mjs');
 
 // MCP harness build — only run if the entry point source exists.
 // The source file is created separately; skip gracefully until then.
-const mcpEntryPoint = './src/mcp-harness/index.ts';
+const mcpEntryPoint = './src/tui-harness/mcp/index.ts';
 
 if (fs.existsSync(mcpEntryPoint)) {
   await esbuild.build({

integ-tests/tui/helpers.ts

@@ -0,0 +1,12 @@
+/**
+ * Re-exports test helpers from the canonical location in src/.
+ *
+ * The canonical implementation of createMinimalProjectDir lives in
+ * src/tui-harness/helpers.ts. This file re-exports it so
+ * that integ-tests/tui/ test files can import from a local path
+ * (`./helpers.js`) without reaching into src/.
+ */
+
+export { createMinimalProjectDir } from '../../src/tui-harness/helpers.js';
+
+export type { CreateMinimalProjectDirOptions, MinimalProjectDirResult } from '../../src/tui-harness/helpers.js';