This PR is **part 2 of 3** splitting
https://github.com/ComposioHQ/composio/pull/3505 to make the removal of
the old 2025 custom tools easier to review. It carries the
**TypeScript** slice.
- builds on top of https://github.com/ComposioHQ/composio/pull/3508
(stacked — review/merge the Python slice first; this PR's base is
`remove-py-custom-tools`)
- removes the legacy `composio.tools.createCustomTool(...)` in-memory
registry: the plural `CustomTools` model, registry wiring, legacy-only
tests/examples/`ts/docs` pages, and stale error/type exports
- preserves the 2026 tool-router APIs: `experimental_createTool`,
`experimental_createToolkit`, `ToolRouter`, `ToolRouterSession`, and
inline custom-tool execution
- regenerates the TypeScript SDK reference so raw tool listing no longer
describes the removed local registry and points to session-scoped custom
tools
- adds a `@composio/core` minor changeset
## Notes
- The committed SDK reference is **verified self-consistent**: `pnpm
--filter @composio/core generate:docs` reproduces it with zero diff.
- This slice is a byte-identical subset of #3505 — the three split
branches recombine to that PR's exact tree. See #3505 for the original
verification logs (`typecheck`, `test`, `lint`, `cf-workers` e2e); CI
re-runs per PR.
Alberto Schiabel