fix(savegame): Load save games on non-Windows builds

[bobtista]

• Closes Save games cannot be loaded on non-Windows builds #3235
• Regression from [GEN][ZH] Fix security issue in map transfer by validating file paths when creating real paths from portable paths #1058

GameState::portableMapPathToRealMapPath lowercases the real path it returns, and getSaveDirectory appends the mixed case Save component, so the two can never match on a case sensitive platform regardless of how the rest of the user data directory is spelled. GameState::isInSaveDirectory then compares that lowercased path with FileSystem::isPathInDirectory, which compares case insensitively only on Windows. On every other platform Save never matches save, GameStateMap::xfer throws on that check, and no save game can be loaded.

Before #1058 the check was path.startsWithNoCase(getSaveDirectory()). #1058 replaced it with the strict containment helper it added for a different purpose, and the case insensitivity was lost off Windows.

Now isInSaveDirectory lowercases both sides before delegating, so the comparison is case insensitive again while the path is still normalized. Windows behaviour is unchanged, the lowercased map name is unchanged, and every caller of isInSaveDirectory is fixed, including the restart path and the map name checks in GameLogic.

FileSystem::isPathInDirectory is deliberately left strict. #1058 added it to validate network supplied portable paths, and ConnectionManager::processFile opens the path it produces with CREATE | WRITE, so its result authorizes a file write and it should keep comparing case sensitively off Windows.

Todo:

• A save game loads on a non-Windows build
• FileSystem::isPathInDirectory is unchanged and still case sensitive off Windows
• A save game loads from the in-game load menu on a non-Windows build
• A save game still loads on a Windows build
• Both games build (z_generals and g_generals)
• A portable path that escapes its base directory is still rejected
• Two directories differing only by case are still treated as different by FileSystem::isPathInDirectory

[OmarAglan]

@codex

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Delightful!

Reviewed commit: d0fa953f49

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