Create "secret path" tool for semi-hidden access to dev island

[felixwalberg]

Add a tool to disable collisions when the player enters the area. Modulates trees within the area to simulate a secret passage within the forest. A possible way for us to style the entry point to Dev Island somewhere in Fray's End (video in comments).

Questions/Concerns/Ideas

• Could we add class_name to the tree scene, or does that introduce too much complexity? My current check if a node is a tree is pretty hacky
• Where all of these should exist filesystem-wise:
  • Where should dev_island.tscn be stored? Among the LoreQuests?
  • Where should (if they are even added) the tree_parter.tscn, tree_parter.gd, and tree_parter_test.tscn be stored?
    • On this thought, should all test scenes be stored somewhere close to dev island?
• Depending on how far the CollisionShape sticks out from the forest border, there is a chance the player gets confused by an invisible border they can't cross (this could be solved by either moving the borders back, rounding out the side so they can walk along more smoothly, etc.)
• The (Quest)Teleporter could exist as a child node of the tree_parter.tscn and could be toggled off when not needed. This would avoid having to drag the teleporter shape into the correct spot, and it would dynamically resize with the tree_parter itself
• We could generalize this to other collision objects (not just trees), but I'm not sure if there is much application there
• This PR should probably not contain the dev island scene itself, but rather just the tree_parter and its testing scene in terms of keeping the scope down

Idea: the entry to the hub can be hidden in Fray's End, but still marked with a sign post for discoverability. Walk across the trees?

Addresses one component of #2108

[felixwalberg]

Screen.Recording.2026-07-07.at.4.50.54.PM.mov

[github-actions]

Play this branch at https://play.threadbare.game/branches/endlessm/dev-island-access/.

(This launches the game from the start, not directly at the change(s) in this pull request.)