fix(maps): repair non-enterable Asteria exits

[zoeyrose]

Summary

Repair the authored Asteria stair that resolves to a non-enterable roof-only
destination, and fix every other equivalent static exit finding reported by
the companion content validator issue #255.

The original report is atrinik/classic#472. It exposed a
stair beside the building containing Gemi that is presented as a usable tiled
transition even though its upper map has no walkable landing.

Known finding

• Source map: maps/shattered_islands/world_7_46
• Source object: stairs_wood_up at (14,5)
• Resolution: last_heal 9 derives tile_path_9
• Target: /shattered_islands/world_7_46_1
• Target condition: roof geometry only, with no usable floor or return stair

Scope

• Run the validator from #255 against the complete
  authored corpus and record every static non-enterable exit it reports.
• Repair all findings that are content defects, including the Asteria stair;
  do not limit the change to the original reproduction if the scan finds
  equivalent invalid stairs, exits, tiled links, or destination coordinates.
• For each finding, choose the intended content behavior explicitly: remove or
  redirect a decorative/invalid exit, or author a valid landing and return path
  where the transition is meant to be playable. Do not make Asteria's roof layer
  playable implicitly just to silence the diagnostic.
• Preserve valid explicit, same-map, tiled, automatic-link, and shop-mat
  transitions and their authored presentation.
• Keep the repair in shared content@main and its Classic-target artifact; do
  not target the historical content-1x line.

Acceptance criteria

• The Asteria stair at world_7_46 (14,5) no longer resolves to an invalid
  roof-only destination.
• Every validator finding is either repaired or explicitly documented as an
  intentional non-player/dynamic case outside the static validator contract.
• The validator reports no remaining static non-enterable authored exits in the
  repaired corpus.
• The normal content validation and Classic-target runtime collection pass
  without modifying authored sources.
• The resulting content behavior is checked in the Classic runtime or an
  equivalent deterministic fixture where practical.

Context

This replaces the server-heavy implementation proposed in
atrinik/classic#507, which is being closed without merge.
The Classic issue and PR should remain linked as historical context; this issue
owns the authored content repair.

Submission checks

• This issue is intentionally separate from the validator implementation.
• The issue contains no credentials, private player data, or undisclosed
  vulnerability details.