t27f R4c: lay the reel's captions, cards and address over the beat video (LR_MODE=5) #10609

Part R4c of epic #10560. Follows R4b.1 (#10603, PR #10605).

Boundary

• specs/t27f/lesson_reel.t27 and its seal .trinity/seals/t27f_lesson_reel.json. Nothing else.
• In scope: a new LR_MODE=5 that lays mode 3's tags, cards, captions and address over the beat video of mode 4, for both orientations.
• Out of scope: the scene clips themselves (R3, t27f: scene renderers for the 12 archetypes and the still anomaly gate (R3) #10592), the render driver, and publishing.

User Scenarios

• An author sets LR_MODE=5 with the voice lengths, then runs the graph with inputs 0..2 as the open, main and close clips, 3..5 as the three phrase wavs and 6 as music. The 15 s reel crossfades the scenes at the beat clock's cuts, with the captions, cards and address of mode 3 on top.
• An author who keeps LR_MODE=3 gets byte-for-byte the graph they had before.

Requirements

• Mode 5 prints one graph per orientation, tall first and then wide, as mode 3 does.
• Each graph is mode 4's beat chain followed by mode 3's overlays. The voice and music input numbers move past the three video inputs.
• Mode 5 refuses a voice that does not fit, as modes 3 and 4 do.
• Mode 3's and mode 4's output is unchanged.
• The input numbering is a function with tests: every input from 0 to music is used exactly once, in both layouts.

Success Criteria

• t27c test-report passes with 0 vacuous tests, and the seal is saved and verified on the Railway lab.
• On the lab, the mode 3 and mode 4 output of the master binary and the new binary for lesson 1 in both languages diffs empty.
• On the lab, ffmpeg renders mode 5 from solid-colour clips, sine phrases and music: 450 frames and 15 s of audio per orientation, and a pixel outside every text box shows red, then green, then blue at the frames beat_solo_frames gives.

Requirements

FR-001: Mode 5 MUST print one graph per orientation, tall first and then wide, as mode 3 does.
FR-002: Each graph MUST be mode 4's beat chain followed by mode 3's overlays, with voice and music input numbers moved past the three video inputs.
FR-003: Mode 5 MUST refuse a voice that does not fit, as modes 3 and 4 do.
FR-004: Mode 3's and mode 4's output MUST remain unchanged.
FR-005: The input numbering MUST be a function with tests ensuring every input from 0 to music is used exactly once, in both layouts.