v2.3.0 — DNS-rebinding SSRF closed; importer redirects checked per hop

Security release: closes a DNS-rebinding SSRF class across every outbound
HTTP call, plus unchecked redirect following in the importers
(PRs #83, #84, #85). Upgrade recommended.

Security

• DNS rebinding. Every caller checked the resolved IP and then called
  fetch(hostname), which resolved again, so a TTL-0 domain could answer
  public for the check and 127.0.0.1 (or cloud metadata) for the
  connection. On the credential paths this delivered the stored bearer
  token (replay), the refresh token and client secret (OAuth refresh),
  and the GitHub token (GitHub spec import) to the internal host. All
  outbound HTTP now goes through src/net/transport.ts, which runs the
  private-range check inside the connection's own DNS lookup, so the
  address checked is the address connected to. Every address in a DNS
  answer must be public.
• Unchecked redirects. The GitHub, SwaggerHub and APIs.guru list
  importers and apitap import <url> followed redirects with no per-hop
  check, so any spec URL could redirect to 169.254.169.254. Redirects
  are now followed hop by hop through the same check, at most 5, only for
  301/302/303/307/308; a Location with userinfo is refused; and
  Authorization, Cookie and Proxy-Authorization are dropped when a
  redirect changes origin.
• read/peek redirect following had no hop limit (a redirect loop never
  ended); it is now capped at 5 (TOO_MANY_REDIRECTS).
• More reserved ranges blocked: multicast 224/4, the documentation
  ranges, 192.0.0/24, IPv4-compatible ::/96, and 6to4 2002::/16.

Changed

• peek reports a DNS failure as a transport error (ENOTFOUND,
  recommendation error) instead of "blocked by SSRF protection".
• OAuth token refresh no longer follows redirects; a redirecting token
  endpoint now fails with Token endpoint returned 30x.
• Replay drops captured content-length, transfer-encoding,
  connection, keep-alive and host headers and lets the connection
  compute them (a captured length went stale once a body template
  expanded).
• read/peek bodies: the size cap counts decompressed bytes and stops
  reading at the cap; a cut never splits a UTF-8 character; stacked
  Content-Encoding is decoded; HEAD and redirects return as soon as
  headers arrive; the response header limit is 64 KB.
• For contributors: tests that intercept outbound HTTP stub
  transport.fetch, not globalThis.fetch.