Add Typed Display Settings Administration

Implements admin-only Display settings with generation-checked
Apply, Save, Load, Defaults, and Reset operations across the web UI,
CLI, SSH dispatcher, and local UI owner. Adds bounded HTTP handling,
session-isolated operation results, browser lifecycle support, and
comprehensive host tests and documentation.

docs/agent/design-decisions.md

@@ -2,6 +2,12 @@
 
 Only constraints supported by implementation or current project documentation belong here. When original rationale is unknown, the entry describes the observable constraint without inventing intent.
 
+## Display configuration has an owner reservation separate from button activity
+
+**Decision (8D.14):** `local_status_ui` owns a nonwrapping RAM config generation and a zero-wait reservation shared by typed Display operations and canonical CLI/legacy Apply. Compare/reserve and publish occur in short timing critical sections; NVS occurs outside them. Save stabilizes selected bytes, Load retains canonical fallback, and Reset commits defaults before RAM publication, including CLI. This replaces Reset's apply/rollback race with failure-before-publication semantics.
+
+**Consequence:** Browser mutations must carry the selected nonzero generation, including Save; never silently replace intervening CLI edits. Buttons and diagnostic holds retain independent activity state, not config generation or persistence ownership. Do not hold timing locks across storage or I2C, add display-presence prerequisites to configuration, or mistake a successful config API for physical panel success. The existing dispatcher carries IDs only; the secret-free slot uses a30-second dequeue admission deadline, not a new timer or hard cancellation. Preserve explicit result uncertainty and no automatic mutation replay. `docs/phase8d14_implementation.md` records the exact contracts and pending target gates.
+
 ## Typed Network edits preserve manager ownership and current secret bytes
 
 **Decision (8D.12/8D.13):** `web_network_settings` admits bounded typed operations into one login-bound slot; the existing dispatcher carries IDs only and calls canonical generation-checked Wi-Fi/mDNS APIs. HTTPD reads only zero-wait secret-free projections. Wi-Fi mutex-local compare/merge/validation preserves omitted PSKs and prevents stale edits undoing CLI/local changes; queue admission precedes RAM publication. Save stabilizes selected bytes under the mutex; browser Wi-Fi Load reads stored configuration only, never generates fallback AP secrets. mDNS uses its own generation and reports RAM-applied/reannouncement-not-queued separately.