Wiki: BACKUP_DIR is documented with no default and a 503 gate that cannot fire

[steilerDev]

[orchestrator] Found by product-architect during a deliberate sweep of the wiki auth/config tables while fixing #1992. Filed rather than fixed there, to keep that issue scoped to the OIDC defect.

Problem

The Backup & Restore section of wiki/Architecture.md states two things that are both false:

1. BACKUP_DIR's default is documented as (none). In fact server/src/plugins/config.ts:259 reads getValue('BACKUP_DIR') ?? '/backups' — there is always a value.
2. It states "Backup functionality is enabled when BACKUP_DIR is set. If unset, all /api/backups/* endpoints return 503." Because the default is unconditional, backupEnabled = !!backupDir (config.ts:288) is always true, so the documented 503 path is unreachable from an operator's point of view.

CLAUDE.md already documents the /backups default correctly, so the wiki is the lone outlier.

Why it matters

This is the same defect class as #1992 — wiki prose describing a gate that the code does not implement — but it is a wrong default plus a dead gate rather than a phantom variable, in a different table. An operator reading this has no way to know backups are on by default, and may believe they have disabled the feature by leaving BACKUP_DIR unset.

Acceptance Criteria

• 1 wiki/Architecture.md documents BACKUP_DIR's default as /backups, matching config.ts:259 and CLAUDE.md.
• 2 The enablement sentence is corrected to describe what actually happens — backupEnabled is unconditionally true — or, if the 503 path is intended to be reachable, that is raised as a code defect in a separate issue rather than documented as if it works.
• 3 A Deviation Log entry records the correction.
• 4 Decide explicitly which of the two readings is right (docs wrong vs. code wrong) and say so on the issue before changing anything. Do not assume the code is correct merely because Wiki documents a nonexistent OIDC_REDIRECT_URI env var and a four-variable OIDC gate #1992 resolved that way.

Notes

• Owner: product-architect (owns the Architecture wiki page).
• Related: Wiki documents a nonexistent OIDC_REDIRECT_URI env var and a four-variable OIDC gate #1992 (same defect class, OIDC tables), Make the authentication rate limits configurable by environment variable #1970/PR feat(auth): make rate limits configurable via env vars #1989 (the work that first exposed this drift surface).