Enforce crash-safe build policy

Add compile-time checks for silent reboot, disabled core dumps, and
disabled debugger-aware panic handling. Include regression coverage,
hardening guidance, and update Phase 8/9 project status.

docs/agent/design-decisions.md

@@ -134,7 +134,7 @@ Only constraints supported by implementation or current project documentation be
 
 ## NVS is persistence, not a physical security boundary
 
-**Decision:** The current firmware stores Wi-Fi credentials and TLS/SSH private keys in unencrypted application NVS. The reserved NVS-key partition does not enable encryption.
+**Decision:** The current firmware stores Wi-Fi credentials and TLS/SSH private keys in unencrypted application NVS. The reserved NVS-key partition does not enable encryption. Phase 9 explicitly excludes secure boot and encrypted NVS by user preference; physical extraction and firmware replacement remain outside the supported threat model, not deferred guarantees of this phase.
 
 **Rationale/evidence:** `partitions.csv`, README security notes, and current code show no NVS-encryption setup. Original rationale for deferring encryption is outside the implementation; the observable limitation is explicit.
 
@@ -142,6 +142,12 @@ Only constraints supported by implementation or current project documentation be
 
 **Relevant files:** `partitions.csv`, `README.md`, `src/web_security.c`, `src/ssh_security.c`, `src/wifi_config.c`
 
+## Supported builds do not export crash memory
+
+**Decision:** Phase 9A requires disabled core dumps and silent panic reboot, and forbids panic/runtime GDB stubs and OCD-aware panic handling. `src/security_build_policy.c` checks resolved SDK configuration at compile time; defaults alone are insufficient. Development, test and production handling profiles share this baseline, with no bypass flag.
+
+**Consequence:** Decoded panic traces/register output are deliberately lost; ordinary boot/status diagnostics remain and are not universally sanitized by this policy. No eFuse, physical JTAG restriction, partition change or retroactive dump clearing is implied. Target panic/recovery validation remains necessary. [Policy and tests](../security_hardening.md).
+
 ## Wi-Fi callbacks enqueue; the manager owns policy
 
 **Decision:** ESP event callbacks copy bounded event data into the Wi-Fi manager queue. A permanent manager task performs driver operations, profile/AP policy, deadlines, reconciliation, and station mDNS announcement transitions. mDNS initializes at most once, remains allocated across transient disconnects while its component handlers withdraw/re-enable the STA interface, and treats failure as nonfatal.