* 🔧 fix: Run Source-Mode Scripts Through tsx

Every source-mode script command died on clean main under the declared
Node >=24 engine before reaching application code: ts-node's vendored
dist-raw ESM resolver, combined with
--experimental-specifier-resolution=node, appended a second extension
to specifiers that already carry one and failed on
@mistralai/mistralai/esm/lib/http.js.js the moment the provider graph
loaded. The scripts now run through tsx, which resolves the tsconfig
path aliases natively with no vendored resolver and no experimental
flag; the paths bootstrap, ts-node, and tsconfig-paths are gone, and
the constrained-heap serializer test spawns its child through
--import tsx instead of the ts-node loader.

Ten script entries pointing at files that no longer exist are removed.
Verified on this branch: the bedrock script reaches a real credentials
error, the openAI cli reaches its conversation loop, and the
128 MiB-heap benchmark passes through the new loader.

Fixes #465

* 📚 fix: Point the Probe Documentation at tsx

Review finding: the context-overflow signatures doc still instructed
the removed ts-node loader invocation.