BRAIDED PATHS (M17): the line forks, wanders, and merges back

USER: branching was single stubs — now the stream braids. A tryBraid
clause (void rotation, weight 0.5) forks the line at a split host: the
main lane runs straight through; the ALT lane is a REAL wandering walk
beside it (offset profile, |do|<=1 per step) that re-enters at a merge
host L=8..14 cells later. Both lanes are genuine channels: the alt lane
realizes through the same WFC, gets its own centerline chain on the
fork window (the diamond alt machinery, flagged braid), its own
channelProxies ribbon, and its own rail.

- BREADTH KNOB (user): per-seed bias rngFamily(seed, 'braid-breadth')
  in 1..3 caps each braid's wander — some seeds run clean, some tangle.
- PER-PEER PRNG lane choice (user): braidLaneAlt draws from each
  racer's own label-derived stream rngFamily(seed, 'lane/idx/seg') —
  independent per peer like pilot personalities; the pack visibly
  splits ~50/50 at forks and rejoins at merges. Physical recovery:
  a shoved marble adopts whichever lane's rail is >0.6u nearer.
  Riders/promotion/respawns are lane-aware; the respawn branch flip
  exempts braid segments (that toggle stays for diamonds/spurs).
- Junction proxies: one flow-symmetric composite for fork AND merge
  (spur junction minus the hole) — deck, far wall, mouth stubs, side
  walls out to the branch port where the alt ribbon takes over. The
  real wedge hazards were ADJACENT vertical-dip pieces: braid spans
  exclude wave/s-curve families near junctions and forks veto non-flat
  approaches.
- Merge law derived: merge = the split mesh z-flipped == rotation+2
  with mirror inverted (asserted in tests). LoopSegment gains
  alt.braid + braidMerge flags.
- Latent M16 fix exposed by the reshuffle: geometry could project
  axially into a reorient window and present mid-roll (world seam a
  marble fell through). Twist windows now claim their flanks and
  world.ts rejects any non-run geometry inside the drum.
- Headless: both lanes of a pinned braid drive clean end to end;
  36-seed invariant scan (fork/merge laws, walk continuity, breadth
  bounds, C0 alt chain, junction proxies); lane-law unit tests
  (determinism, per-racer independence, 30-70 splits). 32-drive stress
  corpus across 16 braid seeds all clean.
- Streams reshuffled: goldens regenerated; scenario pins re-scanned
  (jump-scan-25/grav-scan-33 reorients, jump-scan-12 spur, helix-scan-6
  propeller, grav-scan-25 jump, grav-scan-9 diamond, grav-scan-6
  helix). genVersion unchanged (finite untouched).
162 tests, check clean. Verified in-browser on #marbles: pack rides
through the framed fork, alt lane wanders and rejoins.

commit

7bf56ca6bae407c3ee91af1be0de550cbc41be9b

parent

d255a424051d6c4e8b7561cb7a3a8233a7ba43af

author

Dami <dami.etoile@gmail.com>