Release v0.6.2-esp32: ADR-081 kernel + Timer Svc fix, 4MB CI variant

version.txt → 0.6.2.

firmware-ci.yml: matrix-build both 8MB (sdkconfig.defaults) and 4MB
(sdkconfig.defaults.4mb) variants, uploading variant-named artifacts
(esp32-csi-node.bin / esp32-csi-node-4mb.bin, partition-table.bin /
partition-table-4mb.bin). Unblocks 6-binary releases from CI alone,
no local ESP-IDF required.

CHANGELOG: promote [Unreleased] ADR-081 work into [v0.6.2-esp32],
plus Fixed entries for Timer Svc stack overflow and the
fast_loop_cb → emit_feature_state implicit-decl compile error.

Validation: 30 s run on ESP32-S3 (MAC 3c:0f:02:e9:b5:f8), 149
rv_feature_state emissions, no stack overflow, HEALTH mesh packet sent.

Co-Authored-By: claude-flow <ruv@ruv.net>

firmware/esp32-csi-node/version.txt

@@ -1 +1 @@
-0.6.1
+0.6.2