#2102 set ideRoot during msi installation correctly

[quando632]

This PR fixes #2102

Implemented changes:

• AbstractIdeContext: ideRoot is no longer final; added setIdeRoot(Path) so the context can
  reflect the derived install target.
• IdeContext: added setIdeRoot(Path) to the interface.
• IdeasyCommandlet.installIdeasy(...): after deriving the target via determineIdeRoot(cwd), it
  now calls context.setIdeRoot(...), keeping the whole install run consistent.
• AbstractIdeTestContext: removed the now-redundant ideRoot/ideRootSet fields and
  getIdeRoot/setIdeRoot overrides — the test context inherits the production setter, aligning
  test and production behaviour.
• Added test IdeasyCommandletTest#testInstallIdeasyUpdatesIdeRoot (windows/mac/linux) that fails
  without the fix and passes with it.

Verified the invariants called out in the issue are unaffected: the isIdeRootRequired gate in
applyAndRun, and the temp-download-path creation guarded by ideRoot != null in the constructor.

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Testing instructions

1. Automated: in cli/, run mvn -Dtest=IdeasyCommandletTest test — all cases pass, including
   the new testInstallIdeasyUpdatesIdeRoot. (Reverting the context.setIdeRoot(...) line makes the
   3 new cases fail, confirming the test reproduces the bug.)
2. Manual (fresh setup, e.g. Windows Sandbox where IDE_ROOT is not set): run the IDEasy MSI
   installer, then open the install log at IDE_ROOT\_ide\tmp\ideasy\ideasy\install.log. Confirm the
   Windows Terminal Git Bash configuration succeeds and there is no
   Failed to configure Git Bash in Windows Terminal: null message.

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Checklist for this PR

Make sure everything is checked before merging this PR. For further info please also see
our DoD.

• When running mvn clean test locally all tests pass and build is successful
• PR title is of the form #«issue-id»: «brief summary» (e.g. #921: fixed setup.bat). If no issue ID exists, title only.
• PR top-level comment summarizes what has been done and contains link to addressed issue(s)
• PR and issue(s) have suitable labels
• Issue is set to In Progress and assigned to you or there is no issue (might happen for very small PRs)
• You followed all coding conventions
• You have added the issue implemented by your PR in CHANGELOG.adoc unless issue is labeled with internal
• You have formulated clear instructions on how to test your contribution under "Testing instructions"

[coveralls]

Coverage Report for CI Build 29099695688

Coverage increased (+0.06%) to 72.287%

Details

• Coverage increased (+0.06%) from the base build.
• Patch coverage: No coverable lines changed in this PR.
• 183 coverage regressions across 4 files.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

183 previously-covered lines in 4 files lost coverage.

File	Lines Losing Coverage	Coverage
com/devonfw/tools/ide/context/AbstractIdeContext.java	118	70.32%
com/devonfw/tools/ide/tool/IdeasyCommandlet.java	51	74.76%
com/devonfw/tools/ide/context/IdeContext.java	13	77.78%
com/devonfw/tools/ide/version/VersionSegment.java	1	91.08%

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Coverage Stats

Relevant Lines:	16711
Covered Lines:	12585
Line Coverage:	75.31%
Relevant Branches:	7458
Covered Branches:	4886
Branch Coverage:	65.51%
Branches in Coverage %:	Yes
Coverage Strength:	3.19 hits per line

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💛 - Coveralls