Fixes#11803.
**Problem**
`tool_search` builds a tool's search text from its parameter schema but
never followed `$ref`. MCP servers (Pydantic, FastMCP) often put nested
models in `$defs`:
```json
{ "properties": { "options": { "$ref": "#/$defs/options" } },
"$defs": { "options": { "properties": { "mode": { "description": "reconciliation" } } } } }
```
Search text was `Inspect records options`, so
`tool_search("reconciliation")` found nothing. Durable's copy of
`tool_search` had the same gap. The codemode `resolves to` summary had
the same blind spot for output schemas: a field behind a `$ref` showed
as `structuredContent?` with no field names.
**Fix**
- pi-codemode exports its existing local JSON Pointer resolver as
`resolveSchemaRef(ref, root)`. A malformed percent escape now resolves
to nothing instead of throwing `URIError` (this also affected
`schemaToType()`).
- coding-agent and Durable `schemaText()` follow local `$ref`s. Each
referenced subschema is read once, so recursive and shared definitions
neither loop nor inflate BM25 term counts. Unreferenced `$defs` and
remote refs stay out.
- coding-agent `describeFields()`/`describeUnionFields()` resolve `$ref`
chains against the output schema root.
**Tests**
- `packages/codemode/test/declarations.test.ts`: escaped, remote,
missing, malformed refs.
- `packages/coding-agent/test/tool-search.test.ts`: refs, escaped
segments, recursion and shared definitions, unused definitions.
- `packages/coding-agent/test/suite/agent-session-codemode.test.ts`:
summary through root, field, const, and union refs.
- `packages/durable/test/tool-search.test.ts`: end-to-end load via a
ref'd description; unused definition does not match.
`npm run check` passes.
pi-schema: opt-in coercion, compile(schema, { coerce: true }) with coerce() and
parse(), the superset of TypeBox's Value.Convert rules and pi-ai's old coercion;
unresolvedRefs option; url and json-pointer-uri-fragment formats.
pi-ai: Tool takes any JSON Schema; validation through pi-schema; Type, Static
and TSchema are no longer exported (breaking). pi-agent-core and pi-durable:
tools on pi-schema, no TypeBox dependency. Coding agent: extensions keep Type,
Static, TSchema and StringEnum through an extension view of pi-ai; built-in
tools stay on TypeBox.
- ToolRegistration.deferred: not offered to the model until modelTools names it
- modelTools gains { remove?, add? }; control.addTools writes names to add, so
loaded tools follow the others in load order and a load only appends
- Agent.deferred lists deferred tools not loaded yet
- @earendil-works/pi-durable/tool-search: the coding agent's tool_search (BM25)
- the codemode section leaves deferred tools out
