Route decomposed fields along headlands (Lyrical)

[u33549]

Summary

Ports #119 to the lyrical branch. Completes decomposition-with-route support:
routes decomposed (multi-cell) fields along their headlands so inter-cell
connections follow the shared headland, and fixes a multi-cell headland crash.
Builds on the lyrical ports of #112/#113/#117 (PRs #123, #126, #130).

Changes

Route decomposed fields along headlands

• Previously a decomposed field applied the headland per sub-cell first, leaving
  each cell a disconnected island; per-cell TSP then stitched routes with
  straight-line bridges that cut across the field. Non-TSP modes flattened the
  multi-cell swaths into a single-cell orderer, fanning connections across the field.
• Now: shrink the whole field to a travel ring, decompose it, then shrink each
  sub-cell again for the swath area. genRoute is fed the border-sharing travel
  cells so inter-cell connections follow the headlands.
• generateRouteTSP takes separate travel_cells and swath_cells: small fields
  use a single global genRoute; large fields (swath count above a cap) fall back
  to per-cell TSP to avoid the O(N²) all-pairs OOM.
• Non-TSP route modes combined with decomposition are rejected with a clear
  INVALID_MODE_SET error.
• Decomposed cells and swaths are reused across the swath and TSP branches.

Make the global-route swath cap a parameter

• default_max_swaths_for_global_route (default 300) replaces the hard-coded
  threshold, tunable at runtime via the dynamic-parameters callback.

Fix multi-cell headland crash on collapsed sub-cells

• The multi-cell generateHeadlands(F2CCells) overload applied the headland to
  each sub-cell through the single-Field overload (ending in .getGeometry(0)).
  ConstHL is a negative buffer, so a sub-cell narrower than ~2×width collapses to
  empty and getGeometry(0) threw "Geometry does not contain point 0" on
  decomposed fields.
• Buffer each sub-cell directly, skip cells that collapse to empty, add every
  resulting polygon (a negative buffer may split one cell into several), and throw
  a clear CoverageException if every sub-cell collapses. Generator/width
  resolution extracted into a shared resolveGenerator() helper.

Distro notes (lyrical)

No adaptation from #119 was needed — every touched file is byte-identical to the
rolling base, so the #119 delta applies verbatim. lyrical already uses the
nav2:: (nav2_ros_common) convention (declare_parameter_if_not_declared,
NodeThread) and test_server.cpp already includes <cmath> and <filesystem>.

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