feat(coding-agent): enabled docs:// protocol and custom tool discovery from .omp/tools/

- Added docs:// internal URL protocol handler for accessing embedded markdown documentation files with path traversal validation.
- Added support for executable tool files (.ts, .js, .sh, .bash, .py) in custom tools discovery from .omp/tools/ and .claude/tools/ directories.
- Added generate-docs-index build script to automatically scan and embed markdown documentation files at build time.
- Updated system prompt to document docs:// protocol usage and identify agent as operating within Oh My Pi harness.

biome.json

@@ -44,6 +44,7 @@
 			"!**/node_modules/**/*",
 			"!**/test-sessions.ts",
 			"!**/template.generated.ts",
+			"!**/docs-index.generated.ts",
 			"!**/gen/agent_pb.ts",
 			"!.worktrees/**/*"
 		]