- 16 tools covering Contents, Kernels, Kernelspecs, and Sessions REST APIs
- File upload/download via UserFile, following the Box upload pattern
- Block with operation dropdown, token auth, and 8 catalog templates
- Registered tools + block, generated docs, bumped API validation baseline

…uity, silent notebook fallback

- Route uploads through validateUrlWithDNS + secureFetchWithPinnedIP (matches Grafana/1Password pattern) instead of a raw fetch to the user-supplied server URL
- Replace the upload path/trailing-slash heuristic with an unambiguous directory + filename split
- create_file no longer silently writes an empty notebook when notebook content is malformed JSON — it now errors clearly

encodeJupyterPath now rejects '.'/'..' segments across the whole path
(shared by all 16 tools, not just upload); the upload route returns a
clean 400 when it's hit.

…gaps

- extract the traversal check out of encodeJupyterPath into a shared
  assertion, and apply it to body-only path fields (rename newPath,
  copy copyFromPath, session path) that never flowed through URL
  encoding and so skipped the check
- pass stripAuthOnRedirect to the upload route's secureFetchWithPinnedIP
  call so a malicious Jupyter server can't redirect the PUT to another
  origin and receive the caller's token

A segment like %2e%2e wouldn't match the literal '..' check. Now
decodes each segment before comparing, in addition to the literal
check, so an already-encoded traversal attempt is caught too.

…for HTTP/private-host support and no redirects

The generic external tool executor blocks plain-HTTP and non-localhost
private-IP hosts by default, so every non-upload Jupyter operation
could fail against typical self-hosted setups (LAN IP, docker
hostname, or even literal localhost on a hosted deployment) even
though the upload route worked via its own internal route.

Added /api/tools/jupyter/proxy (DNS-pinned, allowHttp, maxRedirects: 0)
that mirrors the upstream Jupyter response verbatim, matching the
established pattern for self-hosted-arbitrary-host integrations
(Grafana, 1Password) instead of the generic executor path. Each tool's
request block now posts to the proxy instead of building a direct
external URL; transformResponse and outputs are unchanged since the
proxy response mirrors upstream status/body exactly.

Also switches the upload route from stripAuthOnRedirect to
maxRedirects: 0 — stronger, since it stops the uploaded file body
(not just the token) from ever reaching a redirect target.

…separators in upload filename

- The proxy route now independently validates the incoming path field
  for traversal segments instead of only relying on tool-side
  validation before the request reaches it — the route is a shared
  internal boundary, not something only our own tool code can call
- The upload route's fileName can come from an advanced override or
  the legacy fileContent path and could itself contain '/' or '\',
  silently nesting the upload deeper than the directory param
  specified. Now rejected outright before joining.

…-split segment

A segment like foo%2f..%2fsecret has no literal slash, so splitting on
literal '/' first and decoding each piece in isolation treats it as
one opaque segment and never notices the '..' hiding behind the
encoded slash. Decode the full path once, then split and check every
segment the target server's own single URL-decode pass would see.