sharing 1/4: foundations (modes, economy boundary, transfer library)

[keithharvey]

📚 Stacked split of #5704 — review bottom-up

• 1/4 · Foundations (modes, economy boundary, transfer library) (sharing 1/4: foundations (modes, economy boundary, transfer library) #8061) ← you are here
• 2/4 · Transfer runtime (controllers, economy boundary, gadget swap) (sharing 2/4: transfer runtime (controllers, economy boundary, gadget swap) #8062)
• 3/4 · Tech Core / Keystone (sharing 3/4: Tech Core / Keystone #8063)
• 4/4 · Sharing Tab UI (sharing 4/4: Sharing Tab UI #8064)

Each PR merges into the one below it; all four squash-equal the sharing_tab branch (verified byte-identical).

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Stack 1 of 4 splitting #5704 into reviewable layers.

Pure modules + their specs, no runtime wiring yet:

• modes/sharing/* presets, sharing_mode_enums/helpers, modoptions entries
• economy/* — waterfill solver, manual share ledger, shared_config
• team_transfer/* core — enums, comms, shared/synced logic, context_factory, serialization, unit_sharing_categories, tech_blocking
• lua_rules_msg + message framing, i18n interpolate, type defs, shared test builders

Targets the sharing_tab_mergeable integration base. Reviews bottom-up.

[github-actions]

Integration Test Results

14 tests   - 1   6 ✅ ±0   3s ⏱️ ±0s
 1 suites ±0   8 💤 ±0 
 1 files   ±0   0 ❌  - 1 

Results for commit e40bb94. ± Comparison against base commit 5db84d3.

This pull request removes 1 test.

gui_pip/test_gui_pip_autostart_maximize.lua

♻️ This comment has been updated with latest results.