fix(coop): host re-validate craft capacity in SHARED (#121)

[NonPolynomialTim]

Closes #121.

Problem

In SHARED co-op either player can command/edit any craft, so the client-side capacity gate is not enough. A stale-view concurrent edit passes the initiator's gate, reaches the host, and pre-fix the host applied it without re-checking craft capacity — producing an over-capacity craft that can cause a coop desync or a battlescape/deployment fault.

Two host validators were missing the re-check:

• craftRearmValidate validated base/craft/slot/weapon-slot only — none of the four CraftWeaponsState capacity gates (cargo / HWP / storage-items / storage-space).
• soldierArmorValidate validated base/soldier/armor existence only — not Craft::validateArmorChange (STR_NOT_ENOUGH_CRAFT_SPACE).

Fix

• Factored the four inline capacity checks in CraftWeaponsState::lstWeaponsClick into a pure static CraftWeaponsState::equipCapacityError(...) (math is byte-identical to the old block, so host and client can never disagree), and call it from both the UI and craftRearmValidate.
• soldierArmorValidate now re-runs Craft::validateArmorChange host-side, mirroring SoldierArmorState::lstArmorClick.

Both validators funnel host-origin and replica-origin commands through processHostCmd, so the gate now protects every path; a rejected request emits shared_fail and mutates nothing.

Harness fidelity + regression test

• harnessEquip / harnessSetArmor now run the client gate (surfaced as resp["gate"]), matching a real player's screen. A new force param bypasses it to model a stale replica whose gate passed.
• New tools/coop_test/test_shared_capacity_host_gate.py (throwaway mod: an over-capacity craft weapon + a zero-large-capacity Skyranger + a size-2 armor) checks each gate twice:
  • client gate (un-forced): the over-capacity change is refused locally and never sent.
  • host gate (forced past the client gate): the host rejects it (STR_NOT_ENOUGH_CARGO_SPACE / STR_NOT_ENOUGH_CRAFT_SPACE) and both worlds stay unchanged and equal.

Testing

• python tools/coop_test/test_shared_capacity_host_gate.py — both sections green.
• python tools/coop_test/test_shared_equip2.py — all three sections green (no regression from the harness signature change).
• Serial x64 Release build clean.

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