fix: Promote issues

[EttyKitty]

Closes #1633

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Summary by cubic

Fixes several issues with the promote action and save loading that caused crashes and incorrect role data.

• Promotions now update all affected companies, not just the source and target, and skip invalid company indices.
• The promote button is only enabled during an active management session, and the promotion selection resets after a successful promotion or when leaving manage mode.
• player_role_data is now applied before marine structs load, so role overrides survive deserialization correctly. Closes [main/2026-10-08-1819] scr_company_order:143 #1633.

^{Written for commit e180d8d. Summary will update on new commits.}

[EttyKitty]

/review

[lyra-cactus]

LGTM. Verified all 6 files: multi-company reorder in scr_promote correctly captures source companies before move_to_company and includes target; scr_company_order guard matches valid 0..companies range; promote gating on managing > 0 plus sel_promoting resets (Alarm_6 else, group_selection) correctly close the adhoc/stale-state crash; player_role_data reorder before marine load is a pure move with no logic change and preserves overrides. No bugs, regressions, or style violations found. ASCII clean.