fix: mixed filament manual_pattern dependency resolution and delete/merge remap

[zhangzhend0ng]

Summary

Fix dependency resolution and ID remapping for mixed filaments during
physical filament deletion and merge operations, with manual_pattern
properly integrated into the dependency chain.

Changes

Dependency resolution priority

• Unified resolve order: manual_pattern → gradient → component_a/b
• When manual_pattern is non-empty, skip gradient and pair checks
  (pattern already resolves every token, avoiding false positives)

strtoul safety

• Add errno-based overflow detection to all strtoul calls

Token bounds checking

• physical_filament_from_token now validates symbolic "1"/"2" tokens
  against physical filament count

Deletion logic (remove_physical_filament)

• Traverse manual_pattern tokens to detect entries that depend on the
  deleted physical filament
• Adjust pattern tokens of surviving entries (decrement those above
  the deleted ID), including bracket notation [12]→[11] and
  comma-separated groups 34,78→23,67
• Strip stale gradient_component_ids when manual_pattern survives

ID remap (build_filament_id_remap)

• New deleted_mixed_idx parameter: deleted mixed virtual IDs now
  correctly remap to 0 (NONE) instead of being shifted onto survivors
• New mixed_filament_depends_on_physical helper for pattern-aware
  dependency detection
• Merge path correctly zeros out dependents via remap injection

UI fixes

• Delete filament button now delegates to the unified delete_filament
• Show/hide delete button and enable/disable add button correctly
  track physical filament count changes
• Trigger ID remap and UI refresh on mixed filament delete

Tests

• 50+ new regression tests covering serialization, lifecycle, resolve,
  delete (bracket/group/gradient boundaries), merge, and gradient
  encode/decode