[GaganSD]

• Replaced TypeBox builders/validators with @earendil-works/pi-schema@1.5.0 across ask schemas, config validation, answer extraction, and tests.
• Added a small local string-enum helper so tool schemas keep { type: "string", enum: [...] } for Google-style providers.
• Swapped typebox peer/dev dependencies for a pi-schema runtime dependency (8.5 KB gzipped, zero transitive deps), so the dependency count is unchanged, not reduced.
• Preserved schema JSON behavior; the only diff is lit() emitting const without type.
• Verified: npm ci, lint, typecheck, 120 unit tests, 31 integration tests, and the packed artifact smoke build; typebox remains only in historical CHANGELOG lines.