feat: relay hardening — restore build, add tests, negentropy adapter

Restores build broken by eeb9d2d (cvm-relay-stability removed deps):
- CMakeLists.txt: restore display.c, font.c, local_relay.c, relay_selector.c, sync_manager.c, axs15231b, qrcode, wisp_relay
- tollgate_main.c: restore display.h, local_relay.h, relay_selector.h, sync_manager.h includes and display calls
- cvm_server.c: kept master's keepalive/timeout/ping-pong fixes

New test infrastructure:
- test-local-relay, test-relay-nip11, test-cvm-roundtrip, test-cvm-mcp, test-cross-board make targets
- test-cvm-roundtrip.mjs: MCP get_config + get_balance via public relay
- test-cross-board.mjs: cross-board payment test
- test-cvm-mcp-relay.mjs: kept from master

New unit tests (35 tests):
- test_display.c: 22 tests for escape_wifi_field
- test_negentropy_adapter.c: 13 tests for negentropy adapter

New modules:
- negentropy_adapter.c/h: NIP-77 adapter skeleton

Docs:
- AGENTS.md: display module docs, new test commands
- RELAY_HARDENING_PLAN.md: hardening checklist
- RELAY_HARDENING_MERGE.md: merge plan and checklist

Cleanup:
- Removed CHECKLIST-CVM-RELAY.md, PLAN-SQUASH-MERGE.md (stale planning docs)
- Removed components/esp-miner submodule

Host unit tests: 63/63 pass

1 files changed, 0 insertions, 48 deletions

diff --git a/PLAN-SQUASH-MERGE.md b/PLAN-SQUASH-MERGE.md
deleted file mode 100644
index 59eb13e..0000000
--- a/PLAN-SQUASH-MERGE.md
+++ /dev/null
@@ -1,48 +0,0 @@
-# Squash + Merge Plan: feature/cvm-relay-stability → master
-
-## Goal
-Squash the 4 commits on `feature/cvm-relay-stability` into a single commit and
-fast-forward merge into master. All tasks are complete and tested (17/17
-integration tests, 61/61 unit tests, 120s stable relay connection on Board B).
-
-## Checklist
-- [x] Write this plan to markdown
-- [x] Rebase `feature/cvm-relay-stability` onto master
-- [x] Squash 4 commits into 1
-- [x] Fast-forward merge into master
-- [x] Run `make test-unit` — 61/61 pass
-- [x] Push master to remote
-- [x] Remove worktree `/home/c03rad0r/esp32-tollgate-cvm-relay`
-- [x] Delete local branch `feature/cvm-relay-stability`
-- [x] Delete stale backup branches (`backup/master-2cd372c`, `backup/pre-squash-cvm-20260519-010933`, `feature/local-relay-backup`)
-
-## Squash commit message
-```
-feat: CVM relay stability fix + MCP relay integration tests
-
-Relay disconnect fix:
-- TLS read timeout reduced from 15s to 1s (short poll loop)
-- Ping timer fires every 30s independently of read activity
-- Consecutive timeout counter (65s) detects real disconnects
-- Handle relay close frames (opcode 0x08) explicitly
-- Result: 120s+ stable connection (previously ~37s disconnect cycle)
-
-MCP relay integration tests (17/17 pass via `make test-cvm-mcp`):
-- MCP initialize roundtrip via relay.primal.net
-- get_sessions returns session array (0 active)
-- get_usage returns metric/price/step fields
-- Non-owner auth rejection (board silently drops)
-- Owner control request passes after rejection test
-
-Build fixes:
-- Remove display/font/axs15231b deps (from display branch, not in this tree)
-- Add esp_timer to CMakeLists REQUIRES
-
-Host unit tests: 61/61 pass
-```
-
-## Branch commits being squashed
-1. `81885d2` fix: non-blocking WS reads + decoupled ping timer for relay stability
-2. `61fe3ac` fix: remove display deps, add esp_timer to CMakeLists for clean build
-3. `9d701c6` test: MCP relay integration tests — get_sessions, get_usage, non-owner auth
-4. `6c1ccf1` docs: update checklist — all tasks complete