Broken and misdirecting redirects (verified status codes); Agents SDK Security page priority

[briankwest]

Problem

Verified broken or misdirecting URLs (a redirect to a section index or the docs root is worse than a 404 — it looks like it worked):

developer.signalwire.com/sdks/agents-sdk/security/              301 -> signalwire.com/docs        (root)
developer.signalwire.com/sdks/agents-sdk/deployment/production/ 301 -> /docs/server-sdks          (section)
developer.signalwire.com/sdks/agents-sdk/deployment/serverless/ 301 -> /docs/server-sdks          (section)
signalwire.com/docs/agents-sdk/security                         308 -> /docs/server-sdks          (section)
developer.signalwire.com/swml/methods/ai/swaig/functions/       301 -> .../reference/ai/swaig/functions (itself 308s again)
signalwire.com/docs/swml/reference/ai/swaig/functions           308 -> .../reference/calling/ai/swaig/functions
signalwire.com/docs/swml/methods/ai/languages                   404
developer.signalwire.com/guides/voice-and-languages/            301 -> /docs root (drops the reader)
signalwire.com/docs/swml/reference/calling/ai/swaig/defaults    404 (tracked separately: defaults reference page)

Old paths are what search engines still surface, so these are the paths real users travel.

Fix

1. Redirect moved pages to the moved page, never to a section index or the docs root.
2. Priority: the Agents SDK Security page — the page a developer auditing SWML/SWAIG auth most needs, and the one that vanishes most completely.
3. Collapse multi-hop redirect chains (the SWAIG functions path takes two hops through a path that 404s if you stop midway).
4. Add a redirect-integrity check to CI for the top inbound legacy paths.