feat(lighting): add RGB colored light rendering

[zoeyrose]

Summary

• add strict light_color RRGGBB object support, fixed-point RGB propagation, live Python mutation hooks, and colored applied-light behavior while preserving scalar gameplay visibility
• extend MAP2 protocol v1075 with sparse RGB samples and ordered, bounded continuation packets
• render per-channel smooth lighting across ground, walls, roofs, objects, fog boundaries, and linked depths, with coherent discrete fallback and stale-state resets
• add server, protocol, client-state, Python lifecycle, and deterministic pixel-exact regressions

Protocol and compatibility

• Classic protocol advances from 1074 to 1075 and retains exact-version rejection.
• MAP2_FLAG_EXT_LIGHT_RGB follows the complete seven-bit field bitmap and precedes animation data. A zero bitmap resets prior explicit color to scalar gray.
• Full packets declare a uint16_t continuation count; partial packets carry ordered sequence/map/scroll identity. Level payloads are capped at 65,522 bytes so the 7-byte partial header plus 5-byte level frame remain within the 65,534-byte envelope.

Performance and limits

Measurements were taken on this runner at Classic base fca1eb0e and head 52d85b4b; client timings use Release builds and 100 samples after five warmups around the single map_draw_map() call in the frozen 320×240 software-renderer fixture. Server microbenchmarks use the Debug test build, a 21×21 map, and 1,000 iterations.

Surface	Ordinary / before	Colored or dense / after	Bound and interpretation
Frozen full MAP2 fixture	325 B at v1074	327 B neutral; 525 B colored multi-depth	Neutral cost is +2 B (+0.62%) for continuation count; color remains sparse.
Live ordinary room MAP2	11,128 B full; 46 B unchanged; 1,116 B one-tile scroll	2,277 B initial red; 48 B same-level hue change; 37 B neutral reset	Delta-only hue/reset packets remain small; neutral scrolling has no per-tile RGB payload.
Dense 21×21 producer	n/a	116,909 B across 2 payloads; largest 65,487 B	Every payload is below 65,534 B; validation proves ordered complete tile records.
Server source update pair	15.17 µs neutral remove/add	47.21 µs colored remove/add	+32.04 µs per authored colored update; no frame-loop scan is introduced.
Server full rebuild	12.69 µs neutral	28.84 µs colored	+16.15 µs for one radius-13 source on 21×21; work stays source/mask bounded.
Client lighting frame	29.25 ms base neutral	32.97 ms current neutral; 32.77 ms colored	Head is +3.72 ms (+12.7%) versus base and colored adds no further cost in this fixture; bounded below 4 ms regression.
Sample buffers, one 320×240 active depth	308,080 B	615,920 B	+307,840 B; the 307,200-byte RGBA lightmap is unchanged.
Sample buffers, all 13 depths	4,005,040 B	8,006,960 B	+4,001,920 B (3.82 MiB); inactive-depth contexts are freed.
Lit-sprite cache, first frozen frame	1 hit / 3 misses neutral	1 hit / 10 misses colored multi-depth	More unique RGB signatures correctly create distinct entries. Exact signatures are reusable; LRU remains capped at 8 MiB per active depth and inactive-depth caches are freed.

The measured costs are bounded and intentional: neutral wire traffic is effectively unchanged, RGB work is limited to explicitly colored state, and the largest client delta is under 4 ms in the deterministic software-renderer fixture.

Validation

• ./atrinik build all --profile issue-75-colored-lighting --test
• protocol: 2/2 passed
• libatrinik: 14/14 passed, including loopback socket/curl/STUN coverage
• client: 30/30 passed, including map color-state and smooth/discrete pixel-exact player views
• server: 36/36 passed, including lighting, dense MAP2, applied-light, and Python mutation/persistence coverage
• content companion: python3 tools/validate.py passed 89/89
• python3 tools/verify_import_history.py: verified five imported histories
• all changed C headers/sources pass clang-format --dry-run --Werror; git diff --check passes
• isolated topology issue75-colored, profile issue-75-colored-lighting, state scenario-issue75-colored: latest Classic/content heads resolved cleanly, server ready, client completed the QUIC handshake and opened its asset stream; topology stopped afterward

Companion change

• feat(lighting): author colored light sources content#64 adds the exact schema/editor field, representative warm/green/red/blue authored sources, and Python validation/lifecycle coverage on 1.x.

Closes #75

[codecov]

Codecov Report

❌ Patch coverage is 68.46847% with 175 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
libatrinik/map_protocol.c	0.00%	44 Missing ⚠️
server/src/server/light.c	82.42%	8 Missing and 21 partials ⚠️
client/src/client/lighting.c	67.53%	24 Missing and 1 partial ⚠️
server/src/plugins/plugin_python/atrinik_object.c	10.71%	20 Missing and 5 partials ⚠️
client/src/client/commands.c	60.97%	11 Missing and 5 partials ⚠️
server/src/socket/request.c	87.30%	0 Missing and 16 partials ⚠️
client/src/gui/widgets/map.c	80.55%	2 Missing and 5 partials ⚠️
server/src/loaders/object.l	42.85%	1 Missing and 3 partials ⚠️
server/src/types/common/process.c	0.00%	4 Missing ⚠️
libatrinik/packet.c	40.00%	0 Missing and 3 partials ⚠️
... and 2 more

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