[GaganSD]

• Replace typebox schema builders and Value checks with @earendil-works/pi-schema builders and compiled validators.
• Preserve the emitted tool JSON contract: only lit() drops the redundant type key; string enums keep type: "string" for Google providers.
• Swap typebox for @earendil-works/pi-schema as a pinned runtime dependency (1.5.0, zero transitive dependencies); Pi peer set unchanged.
• Update the packed-package load test to resolve the new runtime dependency in isolation.
• Verified: lint, typecheck, unit (148 pass), integration (25 pass), npm ci, build/artifact smoke, and before/after schema JSON diff (only intended lit() type removals).