RFC and ADR guidance lives on one page

Design docs, RFCs & ADRs now holds everything from the Confluence RFCs and ADRs page, so there is one place to check.

• A table shows when to open a pull request only, write an ADR, write an RFC, or write a design document.
• The page defines “architecturally significant” and explains why the ADR bar is lower than the RFC bar.
• RFCs have a status lifecycle, and an RFC needs a risks section alongside its alternatives.
• An ADR must name its trade-offs, and links its RFC instead of copying the alternatives.
• The page carries the only ADR and RFC templates. Repositories copy them into docs/adr/ and docs/rfc/, and Confluence pages paste the same Markdown.
• RFCs and ADRs with no owning repository go under RFCs and ADRs in Confluence.
• ADR statuses are lowercase, matching the template’s frontmatter.
• Design documents use the [TEMPLATE] Technical Design Document - TDD.
• Older Confluence templates, including the previous design document template, are listed as superseded.

The Confluence page now links here.