sharing 4/7: Transfer runtime (controllers, economy boundary, gadget swap)

[keithharvey]

📚 Stacked split of #5704 — review bottom-up

• 1/7 · Transfer library (enums, comms, serialization, test infra) (sharing 1/7: Transfer library (enums, comms, serialization, test infra) #8125)
• 2/7 · Modes & economy boundary (presets, waterfill, share ledger) (sharing 2/7: Modes & economy boundary (presets, waterfill, share ledger) #8126)
• 3/7 · Policies (context → policy → policy_result → action) (sharing 3/7: Policies (context → policy → policy_result → action) #8123)
• 4/7 · Transfer runtime (controllers, economy boundary, gadget swap) (sharing 4/7: Transfer runtime (controllers, economy boundary, gadget swap) #8062) ← you are here
• 5/7 · Tech Core / Keystone (sharing 5/7: Tech Core / Keystone #8063)
• 6/7 · Sharing Tab UI (sharing 6/7: Sharing Tab UI #8064)
• 7/7 · Game modes export (widget, headless startscript, CI workflow) (sharing 7/7: Game modes export (widget, headless startscript, CI workflow) #8095)

Each PR merges into the one below it; together they reproduce the sharing_tab branch (bar one intentional change — index.lua lazy-loads the mode helpers).

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Stack 4 of 7 splitting #5704. Builds on 3/7.

The behavior switch. Replaces the old sharing/restriction gadgets with two unified controllers and routes all team-resource reads/writes through the GG economy boundary.

• add game_resource_transfer_controller (defines GG.GetTeamResources/AddTeamResource/SetTeamShareLevel) and game_unit_transfer_controller
• add cmd_take, allied unit reclaim / partial resurrection / ally geo-mex modes; rename game_disable_assist_ally → game_allied_assist_mode
• delete game_tax_resource_sharing, game_no_share_to_enemy, game_prevent_excessive_share, game_restrict_unit_sharing, game_disable_unit_sharing, game_restrict_resurrection
• migrate all Spring.*TeamResource* call sites to the GG.* boundary
• gadgets/modrules registration, controller spec, in-game test widgets

[github-actions]

Integration Test Results

17 tests  +3   6 ✅ ±0   6s ⏱️ +3s
 1 suites ±0   8 💤 ±0 
 1 files   ±0   3 ❌ +3 

For more details on these failures, see this check.

Results for commit 7504241. ± Comparison against base commit 2fb534e.

♻️ This comment has been updated with latest results.