Resolve issue with duo/trio/quad team forming logic

[SGunner2014]

Add approved & assigned issue number here:

Resolves #4253

Description:

This resolves an issue with duos/trios/quads where humans would be automatically assigned to the emptiest teams, thereby resulting in combinations of humans + nations fighting each other, whereas the preferred behaviour is for humans to be put together where possible.

Please complete the following:

• I have added screenshots for all UI updates
• I process any text displayed to the user through translateText() and I've added it to the en.json file
• I have added relevant tests to the test directory

Please put your Discord username so you can be contacted if a bug or regression is found:

sjg.

[coderabbitai]

Walkthrough

Team assignment now receives explicit Duos/Trios/Quads context. Human placement prefers fuller teams in these modes, and both game assignment and lobby previews pass the new flag. Tests cover legacy behavior and nation pairing.

Changes

Team packing behavior

Layer / File(s)	Summary
Mode-aware team assignment src/core/game/TeamAssignment.ts	assignTeams and lobby previews accept the mode flag and prefer fuller teams for equal friend counts in Duos, Trios, and Quads.
Game and lobby wiring src/core/game/GameImpl.ts, src/client/components/LobbyPlayerView.ts	Game assignment and lobby previews derive and pass the Duos/Trios/Quads flag.
Assignment validation tests/TeamAssignment.test.ts	Existing tests use the explicit non-special-mode flag, and new tests verify human packing and nation placement across mode sizes.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Possibly related PRs

• openfrontio/OpenFrontIO#3994: Both changes modify non-clan player placement in TeamAssignment.ts.
• openfrontio/OpenFrontIO#4596: Both changes modify assignTeams behavior and its team-selection rules.

Suggested labels: Gameplay

Suggested reviewers: evanpelle, developingtom

Poem

Humans gather, nations align,
Duos and Trios form a line.
Quads now pack with thoughtful cheer,
The lobby preview matches what’s near.
Teams find balance, clear and bright.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Linked Issues check	✅ Passed	The changes update team assignment, call sites, and tests to pack humans in duos/trios/quads while keeping explicit counts spread out.
Out of Scope Changes check	✅ Passed	The summary shows only issue-related logic, call-site, and test updates with no obvious unrelated changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Title check	✅ Passed	The title clearly matches the main change: duo/trio/quad team forming logic was updated.
Description check	✅ Passed	The description is directly related to the change and explains the duo/trio/quad team grouping fix.

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[coderabbitai]

Caution

Some comments are outside the diff and can’t be posted inline due to platform limitations.

⚠️ Outside diff range comments (1)

src/core/game/TeamAssignment.ts (1)

107-120: 🎯 Functional Correctness | 🟠 Major | ⚡ Quick win

Put friend groups before friendless humans.

The new tie-breaker cannot preserve a friend pair when a friendless human is processed first. In Duos, [friendless, A↔B] fills the first team with friendless + A, forcing B onto another team. Partition humans with present friends before friendless humans before placement, and add this regression case.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/core/game/TeamAssignment.ts` around lines 107 - 120, The team-placement
flow in TeamAssignment must prioritize humans with existing friends before
friendless humans. Partition or order the input before placement so
friend-connected players are processed first, then add a regression case
covering a friendless player preceding an A↔B pair and verify the pair remains
together.

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Outside diff comments:
In `@src/core/game/TeamAssignment.ts`:
- Around line 107-120: The team-placement flow in TeamAssignment must prioritize
humans with existing friends before friendless humans. Partition or order the
input before placement so friend-connected players are processed first, then add
a regression case covering a friendless player preceding an A↔B pair and verify
the pair remains together.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: be14334f-cc5f-4e20-9b93-807172f79f7a

📥 Commits

Reviewing files that changed from the base of the PR and between ad3fcbe and 4be62af.

📒 Files selected for processing (4)

• src/client/components/LobbyPlayerView.ts
• src/core/game/GameImpl.ts
• src/core/game/TeamAssignment.ts
• tests/TeamAssignment.test.ts

[SGunner2014]

Looking at the review from coderabbit, I can see this is outside the scope of the original ticket because it's behaviour that was already present in the code before I made changes. I can update the PR to include a fix to this flagged issue also, if this is preferred?