Add installed info inventory

[MikeMcQuaid]

Requested in our user survey.

• Let brew info --installed show a readable audit without requiring --json and external filtering.
• Preserve the existing --json --installed path by keeping JSON handling ahead of the new table rendering.
• Cover formulae, casks and Tab install intent so request and dependency reasons remain visible.

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[Copilot]

Pull request overview

Adds a human-readable installed inventory mode to brew info --installed, aligning CLI output with survey feedback while preserving the existing JSON output path when --json is provided.

Changes:

• Make brew info --installed print a readable table of installed formulae and casks (including install intent/reason and source metadata).
• Keep --json --installed behavior intact by handling JSON output before the new table rendering.
• Update manpage/docs/shell completions and add unit tests covering the new inventory output.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
Library/Homebrew/cmd/info.rb	Implements the new human-readable inventory output for --installed and updates the option description.
Library/Homebrew/test/cmd/info_spec.rb	Adds tests asserting the installed inventory output for formulae and casks.
manpages/brew.1	Updates the --installed documentation to describe the new human-readable inventory behavior.
docs/Manpage.md	Mirrors the updated --installed documentation for the website manpage.
completions/zsh/_brew	Updates --installed completion help text to match new behavior.
completions/fish/brew.fish	Updates --installed completion help text to match new behavior.

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