v11: new mmctl shell completion commands for zsh, powershell, and fish

[cwarnermm]

@claude Let's update the Mattermost Product Documentation to reflect the admin's mmctl product experience from Mattermost server v11 onward captured via mattermost/mattermost#31287

Starting from the master branch, ensure the docs PR is added to the v11.0-documentation branch. The doc updates focuses on new mmctl completion commands as follows:
- mmctl_completion
- mmctl_completion_bash
- mmctl_completion_fish
- mmctl_completion_powershell
- mmctl_completion_zsh

[claude]

Claude finished @cwarnermm's task —— View job • claude/issue-8399-20250915-1907 • Create PR ➔

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✅ Updated Mattermost docs for mmctl v11 completion commands

I've successfully updated the documentation for the new mmctl shell completion commands introduced in v11:

Todo List:

• Read repository guidelines (CLAUDE.md) - No CLAUDE.md file found
• Explore documentation structure to locate mmctl command docs - Found at /source/administration-guide/manage/mmctl-command-line-tool.rst
• Research the referenced PR to understand new completion commands - Analyzed existing documentation and identified improvements needed
• Update documentation for the 5 new completion commands - Enhanced all completion command docs
• Test build/lint commands if available - Verified RST syntax is correct
• Commit and push changes - Changes committed and pushed
• Provide PR creation link

Changes Made:

1. Added version information - Added note indicating completion commands are available from Mattermost Server v11.0 onwards
2. Enhanced installation section - Updated to include installation instructions for all supported shells: bash, fish, powershell, and zsh
3. Fixed documentation errors:
   • Corrected fish completion configuration (was incorrectly referencing ~/.zshrc)
   • Fixed powershell completion configuration (was incorrectly referencing ~/.zshrc)
   • Updated powershell code blocks to use proper PowerShell syntax
4. Updated table of contents - Updated description to reflect all supported shells instead of just bash and zsh
5. Added version directive - Added .. versionadded:: 11.0 to the main completion command section

The documentation now properly reflects that these completion commands are new in v11 and provides accurate installation instructions for all supported shells.

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