[SRU] libreoffice 25.8.2 for questing

[Impact]

 * LibreOffice 25.8.2 is in its second bugfix release of the 25.8 line:
     https://wiki.documentfoundation.org/ReleasePlan/25.8#25.8.2_release

 * Version 25.8.1 is currently released in questing. For a list of fixed bugs compared to 25.8.1 see the list of bugs fixed in the release candidates of 25.8.2 (that's a total of 70 bugs):
     https://wiki.documentfoundation.org/Releases/25.8.2/RC1#List_of_fixed_bugs
     https://wiki.documentfoundation.org/Releases/25.8.2/RC2#List_of_fixed_bugs

     25.8.2 RC2 is identical to the 25.8.2 release

 * Given the nature of the project, the complexity of the codebase and the high level of quality assurance upstream, it is preferable to SRU a minor release rather than cherry-pick selected bug fixes.

[Testing]

 * Upstream testing. Bugs fixed upstream typically include unit/regression tests, and the release itself is extensively exercised (both in an automated manner and manually).

  * A recent set of upstream's automated jenkins testing can be found here:
    https://ci.libreoffice.org/job/gerrit_258/792/

  * More information about the upstream QA testing can be found here:
    * Automated tests
      https://wiki.documentfoundation.org/QA/Testing/Automated_Tests
    * Automated UI tests
      https://wiki.documentfoundation.org/Development/UITests
    * Regression tests
      https://wiki.documentfoundation.org/QA/Testing/Regression_Tests
    * Feature tests
      https://wiki.documentfoundation.org/QA/Testing/Feature_Tests

 * Launchpad testing. The libreoffice packages include autopkgtests that were run and verified as passing.
    Tested build can be found at https://launchpad.net/~libreoffice/+archive/ubuntu/libreoffice-prereleases/+sourcepub/17617934/+listing-archive-extra
    * [amd64] https://autopkgtest.ubuntu.com/results/autopkgtest-questing-libreoffice-libreoffice-prereleases/questing/amd64/libr/libreoffice/20251006_150727_aad22@/log.gz
    * [arm64] https://autopkgtest.ubuntu.com/results/autopkgtest-questing-libreoffice-libreoffice-prereleases/questing/arm64/libr/libreoffice/20251006_200752_b6a9b@/log.gz
    * [armhf] https://autopkgtest.ubuntu.com/results/autopkgtest-questing-libreoffice-libreoffice-prereleases/questing/armhf/libr/libreoffice/20251006_191617_a732c@/log.gz
    * [ppc64el] https://autopkgtest.ubuntu.com/results/autopkgtest-questing-libreoffice-libreoffice-prereleases/questing/ppc64el/libr/libreoffice/20251006_142050_b790f@/log.gz (not a regression)
    * [riscv64] not available
    * [s390x] https://autopkgtest.ubuntu.com/results/autopkgtest-questing-libreoffice-libreoffice-prereleases/questing/s390x/libr/libreoffice/20251006_161700_45032@/log.gz (not a regression)
 * General smoke testing of all the applications in the office suite were carried out by going through the manual testplan as documented by: https://wiki.ubuntu.com/Process/Merges/TestPlans/libreoffice

 * Packaging changes are staged at https://git.launchpad.net/~libreoffice/ubuntu/+source/libreoffice/log/?h=wip/questing-25.8

[Regression Potential]

 * A minor release with a total of 70 bug fixes always carries the potential for introducing regressions, even though it is a bugfix-only release, meaning that no new features were added, and no existing features were removed.

 * A combination of autopkgtests and careful smoke testing as described above should provide reasonable confidence that no regressions sneaked in.