Add undo/redo and fix lost edits in the scripting terminal

[rubensworks]

Replaces #78, with the same changes and a clean commit history: every commit is one standalone change. Phase 2 of the scripting terminal UX improvements, and the base of the remaining stack.

I reproduced every problem in a dev client driven by clientdevbridge (or with a unit test that fails on the old code) before fixing it, then checked it again with this branch.

Commit	Problem before	Result with this PR
Add undo and redo to the script editor	A right-click selected the whole 40-line script; one key press replaced it, and that was saved to disk (z). No undo existed.	Right-click no longer selects everything. Ctrl+Z undoes and Ctrl+Y / Ctrl+Shift+Z redo, with consecutive typing grouped into one step (checked: abc, Enter, de undo as 3 steps). History is kept per file. Unit tests added.
Don't echo synced scripts back to the client	The server sent each synced script back. A keystroke typed between the sync and the echo was overwritten: the editor showed aAB but aA was saved.	aAB is saved.
Write scripts to disk atomically	The server's file watcher could reload a half-written file into memory while the server was writing it.	Scripts are written to a temporary file and moved into place. A new unit test saves a 1 MB script 20 times while the watcher runs; it fails on the old code with partial contents. Existing files keep their permissions and new files get rw-r--r-- (a first version used Files.createTempFile, which made flushed scripts rw-------; covered by a test).
Show external script changes in the open editor	After editing the file outside the game, the open editor kept the old text, and the next keystroke wiped the external change from disk.	The editor reloads the new text as an undoable step and keeps the cursor. The external change survives further typing.
Only apply external changes when the file watcher reloads scripts	The watcher also fires on the server's own writes, and its reload replaced everything in memory with what was on disk at that moment. Right after creating a new disk's folder, before the file was written, this made the first script disappear. Two concurrent reloads could also overwrite each other.	The server remembers what it last wrote or read per file, and applies only files that changed outside the mod. Reloads, flushes and script changes now take a shared lock.
Notice all externally created script files	Files created outside the game didn't show up until some other file changed. Each reload cancelled and re-registered the folder watchers, losing events in between, and only folders that already contained scripts were watched. Reproduced in-game: deleting 4 scripts and creating 3 new files (one in a new lib/helpers/ folder) in one shell command left the terminal showing the old list.	All folders of a disk are watched, including empty and intermediate ones, before its files are read; watchers are no longer re-registered; deleted folders are cleaned up. New tests (deletes followed by creates; files in new nested, intermediate and empty folders) fail 3/3 on the old code and pass now. Rechecked in-game.

About the watcher reload commit

I found it because the partial-contents test was flaky: run 15 times in one JVM, it failed 13 times, always observing the script as null. That was this race, not partial contents. After both watcher commits, 30 runs of the whole ScriptingDataTest class had no failures.

Why the atomic write commit is needed

Without it, the external-changes commit caused a regression: typing hello world into a new file gave orld, o worldllhe and rldhello wo, because the editor applied the half-written content that the watcher had read back.

Testing

• Every commit compiles on its own, including tests and Spotless.
• ./gradlew build passes, including the new unit tests.
• ./gradlew runGameTestServer: all 23 tests pass.

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Generated by Claude Code

[github-actions]

Coverage Report for CI Build 39145586285

Coverage decreased (-0.5%) to 47.629%

Details

• Coverage decreased (-0.5%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• 483 coverage regressions across 8 files.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

483 previously-covered lines in 8 files lost coverage.

File	Lines Losing Coverage	Coverage
org/cyclops/integratedscripting/client/gui/component/input/WidgetTextArea.java	215	0.0%
org/cyclops/integratedscripting/client/gui/container/ContainerScreenTerminalScripting.java	143	0.0%
org/cyclops/integratedscripting/inventory/container/ContainerTerminalScripting.java	56	45.9%
org/cyclops/integratedscripting/core/network/ScriptingData.java	40	79.24%
org/cyclops/integratedscripting/client/gui/component/input/TextFieldHelperExtended.java	17	0.0%
org/cyclops/integratedscripting/core/network/GraalScriptFactory.java	5	60.53%
org/cyclops/integratedscripting/network/packet/TerminalScriptingModifiedScriptPacket.java	4	0.0%
org/cyclops/integratedscripting/core/evaluate/ScriptVariable.java	3	81.25%

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Coverage Stats

Relevant Lines:	2815
Covered Lines:	1463
Line Coverage:	51.97%
Relevant Branches:	1002
Covered Branches:	355
Branch Coverage:	35.43%
Branches in Coverage %:	Yes
Coverage Strength:	24.64 hits per line

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💛 - Coveralls