Removed the ability for rails to cross impassible terrain

[TKTK123456]

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Resolves #4902

Description:

Removed the ability for rails to cross impassible terrain
Before:

After:

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tktk1234567

[coderabbitai]

Walkthrough

Rail pathfinding now checks whether the current node is impassable. Traversal stops immediately for impassable sources. Existing water and shoreline rules remain unchanged.

Changes

Rail traversal rules

Layer / File(s)	Summary
Block traversal from impassable nodes src/core/pathfinding/algorithms/AStar.Rail.ts	Neighbor generation evaluates source-node impassability once and passes it to directional traversal checks. isTraversable rejects impassable sources before applying existing terrain rules.

Estimated code review effort: 2 (Simple) | ~10 minutes

Suggested reviewers: evanpelle

Poem

Rails meet a rocky line,
Then stop before they cross.
Water rules still stand,
Shorelines keep their course.
Impassable ground says “no”—
The path now knows the loss.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: preventing rails from crossing impassible terrain.
Description check	✅ Passed	The description directly explains the rail change and links it to issue #4902.
Linked Issues check	✅ Passed	The change rejects rail traversal when the source node is impassible, meeting issue #4902's expected behavior.
Out of Scope Changes check	✅ Passed	The changes are limited to rail pathfinding behavior and are directly related to issue #4902.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

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[coderabbitai]

Actionable comments posted: 1

🤖 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.

Inline comments:
In `@src/core/pathfinding/algorithms/AStar.Rail.ts`:
- Around line 55-86: Add regression coverage in PathFinding.Rail.test.ts for the
rail pathfinding behavior around isTraversable: verify an impassable source, a
passable node adjacent to an impassable node, and a route that would otherwise
cross impassable terrain. Keep the existing adjacent land-to-land case and
assert that impassable nodes are never included in returned paths.

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Fix all unresolved CodeRabbit comments on this PR:

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 35f0deb9-5007-4dde-a217-2f4d767e1bf3

📥 Commits

Reviewing files that changed from the base of the PR and between e08c64c and 63ad719.

📒 Files selected for processing (1)

• src/core/pathfinding/algorithms/AStar.Rail.ts

[FloPinguin]

thanks