[18 India] Fix TR home token blocked when Nepal is full (#11379)

[ddaybell]

Summary

• When NCR places in one Nepal (M10) city and EIR uses Danish EIC (P5) in the other, TR could not float - both city slots were consumed and TR's home token had nowhere to go
• Root cause: Danish EIC's cheater flag bypassed TR's tile-level reservation check in tokenable?, taking the last open slot
• Fix: add G18India::Step::SpecialToken that overrides process_place_token; when a cheater token ability would bypass a tile reservation block, it sets @extra_slot = true on the ability before calling super, routing the token to @extra_tokens instead of consuming the reserved slot
• TR's tile-level reservation is preserved, so TR's home token placement (via the pending-tokens player-choice mechanism) continues to work normally

Closes #11379

Test plan

• All 133 existing 18 India fixture tests pass
• Manually verify a game where Nepal gets filled before TR floats - TR should be able to place its home token in the remaining open city

?? Generated with Claude Code

[perwestling]

I looked at this and it looked good to me. But I also made a test and let an LLM review it.

Here is what the LLM (Mistral) thought about the PR:

Code Review: PR #12705

Overall: LGTM ✅

Analysis:

• Clean, minimal fix (2 files, 28 lines)
• Correctly identifies the root cause: Danish EIC's cheater flag bypassing TR's reservation
• Elegant solution using existing @extra_slot mechanism
• Well-commented code explaining the logic
• Preserves TR's tile-level reservation

One suggestion:
Consider adding a specific fixture test that reproduces the bug scenario:

1. NCR places in Nepal city 1
2. EIR uses Danish EIC (P5) in Nepal city 2
3. TR floats and places home token successfully

Testing:

• All 133 existing 18 India fixture tests pass ✅
• Manual verification recommended for the specific scenario

Approval: Ready to merge 🚀

Remove AI assisted approval.