[ump45nose]

Description

--theme accepts default as a special value, but it is missing from the "Special values" list in the man page.

• src/theme.rs:138-145 — ThemeName::new maps the literal string "default" to ThemeName::Default, so --theme=default / BAT_THEME=default is not a theme name lookup.
• src/theme.rs:30-35 — default_theme(ColorScheme::Dark) is "Monokai Extended".
• src/theme.rs:420-433 — the test default_dark_if_requested_explicitly_through_theme asserts that an explicitly requested ThemeName::Default resolves to the dark default theme for every detected color scheme, i.e. it does not adapt to the terminal.
• The value is already used in the documentation that never defines it: README.md:738 shows bat --theme=default "$@".

The entry is added after light, matching the surrounding .IP style. Along the way this fixes a duplicated "where" on the auto:always entry (assets/manual/bat.1.in:187).

No changelog entry: CONTRIBUTING.md states one is not necessary for documentation updates, and the note there says the verifying workflow failure can be disregarded in that case.

Only assets/manual/bat.1.in is touched. The rendered bat.1 is gitignored (.gitignore:14) and produced at build time from this template by build/application.rs:42-43, and doc/long-help.txt is the --help snapshot checked by tests/integration_tests.rs:868 — both are generated from other sources, and the same special-values list in clap_app.rs:429-441 also omits default. I left the --help text alone to keep this to one file; say the word if you would rather it be extended there as well.

Checklist

• Used the existing code style — the new entry reuses the .IP / prose form of its neighbours.
• Added a changelog entry — not required for docs per CONTRIBUTING.md.
• Confirmed that all relevant tests pass — docs-only change to a roff template; no Rust code and no clap_app.rs token was touched, so cargo test cannot be affected. I could not run cargo in my sandbox (the command was blocked by the environment), so this rests on the diff being template text only.
• Confirmed that all relevant documentation was updated — this is the documentation fix.

Overlap: the open PRs editing nearby man-page text are #4012 (-b, --number-nonblank), #4086 (nonblank numbering), #4009 (BAT_WIDTH), #4078/#4077 (--fallback-syntax, --sanitize) and #4033 (grammar in the --style/--paging passages, plus clap_app.rs); none of them modify lines 181-194.

AI assistance disclosure: an AI tool was used to diff the man page against src/theme.rs and to locate the README.md:738 usage; I reviewed the enum, the constant and the test myself and can answer questions about the roff and theme semantics.