[dsl] Remaining §8.8 movement actions are not lowered though the matrix says Exec In (follow_lane, follow_path/trajectory, keep gaps, …)

[JArmandoAnaya]

What

The DSL lowering dispatch (frontends/dsl/src/lower.cpp:467-588) implements exactly seven §8.8 names (assign_speed, change_speed, remain_stationary, assign_position, vehicle.change_lane, change_space_gap, change_time_gap) plus three no-op generics. The coverage matrix marks these as Exec In although they never reach the dispatch:

• assign_orientation (§8.8.2.5), change_position (§8.8.2.11), keep_speed as an action (§8.8.2.13)
• follow_path / follow_trajectory (§8.8.2.16-.17) — "→ p2-s5 trajectory machinery" is not wired, though the runtime machinery exists
• follow_lane (§8.8.3.2)
• keep_time_gap / keep_space_gap (§8.8.3.13-.14) — lower.cpp:569 says outright "the continuous form is not lowered yet", though the runtime's continuous LongitudinalDistanceAction exists
• assign_position by route point / OpenDRIVE point (§8.8.2.4) warns "not lowered yet" (lower.cpp:497-500) while the matrix row is flatly In
• map.set_traffic_lights_control_file (§8.12.2, declared stdlib.cpp:964) is silently ignored — only set_map_file is special-cased (lower.cpp:1539); absent from the matrix entirely

Also: gap_direction lateral members are coerced to a longitudinal keep the scenario never stated (lower.cpp:561-565 warns, then proceeds) — against the matrix's own "never silently dropped/altered" contract.

Done when

For each name: lowered onto the existing runtime action (most have one — trajectory follower, continuous distance keeping, teleport/orientation) with dsl_lowering_test.cpp coverage, or the matrix row flipped to Post with a structured UnsupportedFeature diagnostic and this issue as owner. gap_direction stops synthesizing unstated behavior (report instead). Matrix summary counts recomputed.