phase: 02_tls_control_channel

**Verified / implemented (phase 02 final pass)**
- All 6 tasks already in `complete/` → verification pass. Device measurement **found a real defect (README bug 11)**: the cert carried its SAN *value* under the OID written from the ASCII text `"2.5.29.17"` instead of DER content bytes `55 1D 11` (`openssl x509 -text` showed `1.10.46.53…`, hex `30 2f 06 09 32 2e 35…`), i.e. **no SAN** → hostname validation impossible while every host check stayed green (they walked the value, never the label).
- Fixed in the pure module: `kSanOidTlv`/`sanOidDer()`, `sanExtensionFullDer()` (pinned to the 43 bytes OpenSSL writes for these names), `derCarriesSan()` (OID *and* value); `tls.cpp` uses them + 3 `static_assert`s; `cert` now warns and names the remedy. 33 new checks in `test_tls_pem.cpp`, incl. the pre-fix extension byte-for-byte (`derContains` yes / `derCarriesSan` no).
- Corrected a false finding: the earlier "fingerprint rotated once" was an **OpenSSL `-ext` artifact** (`C8:76…` vs the real `61:54:19:30…`, same DER). Re-measured: serial `cert` == live handshake DER hash; page 51 626 B, `sha256 dd16e195…f04e9` == locally assembled page.

**Tests / lint (100 % green)**
- `bash .agents/validate.sh` → **GATE_EXIT=0**: `RESULT: all suites passed` in the plain *and* `SANITIZE=1` run, **4826 checks / 0 failures** each; `bridge`/`console`/`rollback` **SUCCESS**; `page bytes: 51626`; `README/AGENTS claims: OK`; `repo hygiene: OK (71 tracked files)`.
- Footprint: bridge **RAM 30.4 % (99 616 B) / Flash 39.6 % (1 246 145 B)** vs baseline 26.7 %/87 592 & 36.1 %/1 135 293 → **+12 024 B RAM / +110 852 B flash**; TLS alone +6 160 B / +100 008 B (rollback image byte-identical); session heap 187 936 → ~145.5 k (1 session) → ~107.9 k (2).
- `ruff check --select F,E9 tools/ tests/` → All checks passed; `bash -n` clean (gate, runner, probe); `-Wall -Wextra` warning-free.

**Completion criteria**: 1 ✓ (gate green + RAM/Flash + session heap quoted); 2 ✓ as recorded (boot prints no fingerprint on the NVS-load path, `cert` prints on demand, identity survived reflashes, nothing about the key is printed anywhere — `nvs erase`→first-boot leg **not re-run**); 3 ✓ re-measured (51 626 == gate; `:80` → 301, no page bytes); 4 partial — 426/401/404 + pinning handshake measured, but arming/typing needs the operator's passphrase (`dflt:0`) and the target is this machine, so no input was sent; 5 ✓ (no `.pem/.key/.crt` tracked or on disk; hygiene block ran); 6 ✓ (`[env:rollback]` built every run + README section); 7 ✓.

**Documentation**: README — check count 4793→4826 (intro + Quick start), `test_tls_pem` 829→862 with new pins, footprint/TLS-cost rows re-measured, "Ten bugs"→"Eleven bugs" + new entry + both anchors, `cert` row, Troubleshooting names-warning row, `tls_pem.h` architecture entry, nine/ten pure-module wording. AGENTS.md (staleness only): "Ten bugs"→"Eleven bugs" ×2, 4826, and the certificate-names row extended with the DER-OID rule. `.agents/HW_VERIFICATION.md` — 426 body/headers re-measured, fingerprint row correction + `-ext` rule, new SAN row (`failed → fixed in tree, device leg needs nvs erase`) with closing commands; phase report written to `.agents/reports/02_tls_control_channel/02_tls_control_channel__00_phase.a1.md`.

**Deviations / live-infra**: made **no** reflash and **no** `nvs erase` (erase also destroys the token and Wi-Fi credentials; flashing puts a live HID keyboard into ROM download mode on this machine). Live steps were read-only `curl`/`openssl` plus one capped `console.py cert` (opening the CDC resets the board — permitted, recorded). No phase/PLAN files touched; everything left in the working tree for the harness to commit.

**Next pending phase**: `03_session_takeover` — `01_pending_claim_socket.md`.

platformio.ini

@@ -50,6 +50,12 @@ lib_deps =
 build_flags =
     ${usb.fs_include}
     -DARDUINO_USB_MODE=0
+    ; TLS on: the page and the WebSocket are served over HTTPS/wss with an identity the
+    ; board generated itself (src/tls.h). The rollback value is KR_TLS=0 -- plain http://
+    ; and ws:// only, exactly the pre-phase-02 behaviour, same standing as `mouse off`.
+    ; It is a compile-time switch because a device that cannot be reached over TLS after a
+    ; bad provisioning change needs a way back that is a reflash, not a repair.
+    -DKR_TLS=1
     ; CDC_ON_BOOT=0 is what makes the Logitech identity possible: with 1,
     ; cores/esp32/main.cpp calls USB.begin() from app_main() before setup() runs, the
     ; first tinyusb_init() fixes the VID/PID/strings as Espressif's, and every
@@ -79,3 +85,31 @@ build_flags =
     ${usb.fs_include}
     -DARDUINO_USB_MODE=1
     -DARDUINO_USB_CDC_ON_BOOT=1
+    ; Same TLS default as bridge: the control plane is what this environment exists to
+    ; diagnose, so it must behave identically. Roll back with -DKR_TLS=0 (see env:rollback).
+    -DKR_TLS=1
+
+; ---------------------------------------------------------------------------
+; Rollback: the bridge with TLS compiled out, i.e. the pre-phase-02 build -- plain
+; http:// page and ws:// socket on :80, no :443, no identity in NVS. PLAN.md locks this
+; in as the way back from a provisioning change that left a board unreachable over TLS:
+; the fix is a reflash, not a repair, and a way back only counts if it still builds.
+; That is why it is an environment and not a remembered command line: `pio run` has no
+; --build-flags option in this PlatformIO, and a second -DKR_TLS on the command line
+; beside the -DKR_TLS=1 above is a macro redefinition whose winner depends on flag order.
+; Unflagging the default and setting 0 is the only spelling with no ambiguity -- and
+; .agents/validate.sh builds this env on every run, so the rollback cannot quietly rot.
+;
+; Nothing about arming moves here: KR_TLS changes which port carries bytes, never who may
+; type (src/config.h, README "The rollback"). The page this image serves is the KR_TLS=0
+; branch of the marker in src/web_page.h; it is the only build where a plaintext ws://
+; session is the normal case, and the only one the README permits it in.
+; ---------------------------------------------------------------------------
+[env:rollback]
+extends = env:bridge
+build_flags =
+    ${env:bridge.build_flags}
+    -DKR_TLS=0
+build_unflags =
+    ${env:bridge.build_unflags}
+    -DKR_TLS=1