chore(deadcode): remove unused helpers and constants

[duriantaco]

This replaces the earlier stale dead-code branch with a narrower, verified cleanup pass against current develop.

Removed:

• unused helpers, aliases, and imports in
• unused experimental decision tree in
• unused constant in
• unused constant in

Deliberately not removed in this pass:

• callback / protocol / interface-shaped items such as , , , , and
• other lower-confidence public-surface candidates

Validation:

• ..............ss...........s............................................ [ 56%]
  ....................................................... [100%]
  124 passed, 3 skipped in 11.18s
• Warning: Unable to set locale. Expect encoding problems.
  {"now": {"iso": "2026-04-06T14:48:28+08:00", "custom": "2026-04-06 14:48:28 +08"}, "cpu": {"total": 45.2, "user": 30.0, "nice": 0.0, "system": 31.1, "idle": 38.9, "ctx_switches": 6317, "interrupts": 123359, "soft_interrupts": 612274017, "syscalls": 68977, "cpucore": 8}}