Add Phase 9C security hardening

Generate exact-hash SDK source overrides without modifying dependencies.
Harden
SSH allocation and algorithm policy, tighten web authentication cleanup,
and add
focused host contract tests and documentation.

tests/ssh_memory/README.md

@@ -0,0 +1,59 @@
+# SSH memory hook tests
+
+Run from the repository root:
+
+```sh
+CCACHE_DISABLE=1 python3 tests/ssh_memory/run.py
+```
+
+Optionally verify the installed, audited SDK source contract too (no downloads):
+
+```sh
+CCACHE_DISABLE=1 python3 tests/ssh_memory/run.py --idf-path /home/mscholz/.platformio/packages/framework-espidf
+```
+
+The runner compiles the actual `src/ssh_memory.c` and extracts the actual volatile
+`secure_wipe()` body from `src/secure_random.c`. Only SDK headers and heap calls
+are doubled. Temporary build files stay outside the repository. `CC` and `CFLAGS`
+are supported; the runner also forces `CCACHE_DISABLE=1` for child processes.
+
+Coverage:
+
+- NULL free, malloc/realloc NULL and zero-size delegation, secure zero-size free.
+- Rounded usable capacity larger than the original request; whole-capacity wipe
+  checked **before** the fake heap actually frees the backing allocation.
+- Equal-capacity and shrink pointer retention, discarded-tail wiping, unchanged
+  prefix, retained capacity and logical regrowth without allocation.
+- Growth copies every byte of the old usable extent, including rounding, without
+  over-copying into the new suffix. Both allocations are live during growth.
+- PSRAM-first/internal-fallback capability order on every allocation; successful
+  fallback and migration back to preferred PSRAM on a later growth.
+- Failed allocation/growth leaves the old pointer and full contents live and
+  unchanged, with no SDK realloc fallback (none is supplied by the test).
+- Base-pointer-only extent queries, live-pointer checks, aligned payloads and
+  prefix/suffix guards, request sizes unchanged including `SIZE_MAX`.
+- Six rejected poisoning configurations, explicit-zero inactive options, and
+  four rejected IDF versions. The supported profile is unpoisoned IDF 5.5.0.
+- Optional exact normalized function-body contracts for installed heap extent
+  queries/TLSF size accessor, public declaration and implementation alias; compile
+  the module with the installed IDF version header. This is a narrow source
+  contract check, not execution of the target SDK heap or a complete heap audit.
+
+## Integration and limits
+
+The parent must add `ssh_memory.c` to its build and register these three hooks
+before wolfSSH/wolfSSL allocations begin. This change does not integrate them.
+
+There are no production headers preceding allocations, metadata tables, locks or
+additional tasks. Allocator alignment and allocation-size failure semantics are
+preserved by passing the size straight to `heap_caps_malloc_prefer()`. A shrink
+retains capacity rather than reclaiming heap; growth temporarily needs old plus
+new allocations. PSRAM remains preferred, but internal fallback can transiently
+need the full new allocation while the old one is still live. No runtime reserve
+or hardware performance claim follows from these host tests.
+
+Heap poisoning is deliberately unsupported: its canary layout is not compatible
+with blindly wiping a rounded extent. The version guard requires re-audit on SDK
+updates. Cleanup covers retired allocations and explicit realloc tails, not
+still-live library buffers, parser spans, stack temporaries or all library
+secrets. Hardware validation is deferred to whole-phase testing.