feat(config)!: one AGENTIC_KIT_ knob header, one SDK-wide log ceiling

[heshaoqiong-tuya]

Summary

Every build-time knob in the SDK now lives behind an AGENTIC_KIT_ prefix, with its
default and rationale in its owning subsystem's config file — there is no central
entry file. Logging collapses to one compile-time ceiling for the whole SDK.

Knobs	File
Log ceiling + integrator-override pickup	common/log.h
PAL FreeRTOS task sizing (3)	pal/pal_config_defaults.h
MQTT + ATOP-over-HTTP (6)	modules/iot-client/include/iot_client_config_defaults.h
TAI buffers & scheduling (9)	modules/rtc-tcp-client/include/tai_config_defaults.h
— none by design (see banner)	modules/tuya-ble/include/tuya_ble_config_defaults.h

The override pickup lives in common/log.h because every SDK translation unit includes
it: whichever defaults header a TU reaches first, the integrator's overrides are applied
before any #ifndef default. Each *_config_defaults.h includes log.h first for
exactly that reason, so include order can never matter.

Breaking changes

1. All 20 knob macros renamed with the AGENTIC_KIT_ prefix. The old names collided
for real: coreMQTT's own core_mqtt_config_defaults.h defines a same-named
MQTT_SEND_TIMEOUT_MS (20000U) that fought the SDK's 2000U default by include order, and
LOG_LEVEL is claimed by several platform SDKs. Migration is a mechanical rename:

Old	New
LOG_LEVEL / TAI_LOG_LEVEL	AGENTIC_KIT_LOG_LEVEL (one ceiling for the whole SDK)
MQTT_MAX_PACKET_SIZE	AGENTIC_KIT_MQTT_MAX_PACKET_SIZE
MQTT_SEND_TIMEOUT_MS	AGENTIC_KIT_MQTT_SEND_TIMEOUT_MS
MQTT_RECV_TIMEOUT_MS	AGENTIC_KIT_MQTT_RECV_TIMEOUT_MS
MQTT_CONNECT_TIMEOUT_MS	AGENTIC_KIT_MQTT_CONNECT_TIMEOUT_MS
REQUEST_HEADER_BUFFER_SIZE	AGENTIC_KIT_REQUEST_HEADER_BUFFER_SIZE
RESPONSE_BUFFER_SIZE	AGENTIC_KIT_RESPONSE_BUFFER_SIZE
TAI_FRAG_BUF_SIZE	AGENTIC_KIT_TAI_FRAG_BUF_SIZE
TAI_MAX_FRAGMENT_PAYLOAD	AGENTIC_KIT_TAI_MAX_FRAGMENT_PAYLOAD
TAI_TX_HDR_BUF_SIZE	AGENTIC_KIT_TAI_TX_HDR_BUF_SIZE
TAI_FRAME_COALESCE_LIMIT	AGENTIC_KIT_TAI_FRAME_COALESCE_LIMIT
TAI_TX_CTRL_BUF_SIZE	AGENTIC_KIT_TAI_TX_CTRL_BUF_SIZE
TAI_MAX_ATTRS	AGENTIC_KIT_TAI_MAX_ATTRS
TAI_DRAIN_BUDGET_MS	AGENTIC_KIT_TAI_DRAIN_BUDGET_MS
TAI_WORKER_POLL_CAP_MS	AGENTIC_KIT_TAI_WORKER_POLL_CAP_MS
TAI_LOG_MEDIA_SAMPLE_N	AGENTIC_KIT_TAI_LOG_MEDIA_SAMPLE_N
PAL_FR_TASK_STACK_WORDS	AGENTIC_KIT_PAL_FR_TASK_STACK_WORDS
PAL_FR_TASK_PRIORITY	AGENTIC_KIT_PAL_FR_TASK_PRIORITY
PAL_FR_TASK_NAME	AGENTIC_KIT_PAL_FR_TASK_NAME

2. One compile-time log ceiling. AGENTIC_KIT_LOG_LEVEL (0=none … 4=debug, default 4)
gates every SDK log macro — iot-client's log_* family, TAI_LOG*,
TUYA_BLE_HAL_LOG*, and the coreMQTT/coreHTTP log routing. Above the ceiling a log line
compiles out entirely: no call, no argument evaluation, no format string in the image.
Below it, the existing runtime filter (log_set_level()) still applies. Module macro
names and output bytes are unchanged (thin re-tags). -DTAI_LOG_LEVEL=N moves to
-DAGENTIC_KIT_LOG_LEVEL=N, noting it now silences the whole SDK.

Also removes the dead IOT_DO_NOT_USE_CUSTOM_CONFIG flag from the ESP-IDF component.

How integrators override (unchanged story, one file reaches everything)

1. Recommended — create your own agentic_kit_config.h holding only the knobs you
   want to change (plain #define, no #ifndef), put its directory on the include path
   of every target that compiles SDK sources. Picked up automatically via __has_include,
   before every default — the lwIP lwipopts.h / mbedTLS mbedtls_config.h pattern.
2. -D<NAME>=<value> per knob.
3. -DAGENTIC_KIT_USER_CONFIG='"my_opts.h"' — arbitrary file name, for toolchains
   without __has_include; when set it wins and the include-path search is skipped.

The SDK never owns a file named agentic_kit_config.h: a quoted include searches the
includer's own directory before the -I path, so the plain name must stay the
integrator's. All knob defaults use #ifndef, so unlisted knobs follow SDK defaults and
upgrades merge cleanly.

Why this shape

• Buffer sizes are product properties (DP schema size, PSRAM or not, audio frame
  length) — the defaults now sit in the subsystem a reviewer audits for them, each with
  its full rationale (units, couplings, war stories) in the file's comments.
• One pickup point (common/log.h) keeps the "one override file for everything" story
  while the defaults themselves are distributed — no per-module override files needed.
• Iron rule: knob values must be identical across every target that compiles SDK
  sources (struct layouts and buffer sizes depend on them; mismatches fail silently).

Full guide — mechanisms, ESP-IDF/CMake wiring, two-layer log model, per-knob tables,
migration: docs-site/docs/guides/compile-time-knobs.md.

Verification

• cc -dM: all 19 knob macros byte-identical to the pre-change single header (only
  include guards differ); knob values and rationale comments preserved.
• One agentic_kit_config.h on the include path overrides LOG_LEVEL / MQTT / TAI /
  ATOP / PAL knobs simultaneously; AGENTIC_KIT_USER_CONFIG wins over it; C++ TU
  compiles and links (config sits outside extern "C").
• Fresh CMake build + ctest: 15/15 at defaults and with an integrator override
  file on the include path; LOG_LEVEL 0–3 compile warning-free, level 0 strips every
  _log_emit reference and log tag string from every object (sole documented exception:
  the tai_pkt_log.c media sampler).
• Docs site builds clean; three-lens adversarial review (include order, doc pointers,
  behavior preservation) — all findings addressed.