krino: coloured output, and --no-color

Lukasz, 2026-09-14: colour the output for ease of reading, with an option of
no colour. Section 8.2 now lists what is styled, from the 16-colour ANSI palette
plus bold and faint only, so the terminal theme decides the look; section 11
adds --no-color; section 15 adds the colour tests.

1 files changed, 26 insertions, 3 deletions

diff --git a/docs/design.md b/docs/design.md
index 153bab0..82168e5 100644
--- a/docs/design.md
+++ b/docs/design.md
@@ -1,7 +1,8 @@
 # krino design
 
 Status: describes krino 0.0.1, 2026-09-13; amended 2026-09-14 for 0.0.2:
-duplicates are never deleted (§5.5).
+duplicates are never deleted (§5.5), and coloured output with `--no-color`
+(§8.2, §11).
 
 krino (from Greek κρίνω, "to separate, to judge, to decide") sorts files in
 chosen directories by rules. A rule tests a file's type, name, path, size,
@@ -424,8 +425,26 @@ not acted on: 3 busy · 12 ignored · 210 unmatched   (-v lists them)
 [a] apply all   [c] choose per file   [s] skip this directory   [q] quit
 ```
 
-- Colours use the terminal's ANSI palette, only on a terminal, and never
-  when `NO_COLOR` is set. Permanent deletes are always marked in capitals.
+- Colours use only the terminal's 16-colour ANSI palette plus bold and
+  faint, never 256-colour or RGB values, so the terminal's theme decides what
+  they look like. They appear only on a terminal, and never when `NO_COLOR`
+  is set or `--no-color` is given. What is styled:
+
+  | Element | Style |
+  |---|---|
+  | directory header `krino: NAME  PATH`, and `krino: undo RUN` | bold |
+  | `copy`, `move`, `rename` | green |
+  | `trash` | yellow |
+  | `DELETE permanently`, and undo's `refused:` | bold red |
+  | a skipped step, and a match reason | faint |
+  | rule name | blue |
+  | the `warnings` heading and its lines | yellow |
+  | outcome line | the applied count green when above 0, the failed count red when above 0 |
+  | prompt keys `[a]` `[y]` … | bold |
+  | `krino log`'s `(undone)` | faint |
+
+  Permanent deletes are always marked in capitals, so they stand out without
+  colour too.
 - A plan taller than the terminal is shown through `$PAGER` (default
   `less -FRX`) and the prompt follows when the pager exits.
 - Keys are read one at a time without Enter.
@@ -519,6 +538,7 @@ krino undo [RUN]            reverse a run (default: the last one)
 -v            also list unmatched, ignored and busy files; full match reasons
 --json        with -n: the plan as JSON (format unstable before 1.0)
 -c FILE       use FILE instead of ~/.config/krino/krino.conf
+--no-color    never colour the output, as when NO_COLOR is set
 -h, --help    help
 --version     print "krino 0.0.1"
 ```
@@ -652,6 +672,9 @@ placeholder numbers, screenshots by date, cleaning up old installers).
   originals differ. Each case plans and applies in a temporary directory and
   checks that every copy is still on disk.
 - **CLI:** golden files for plan rendering without colour; exit codes.
+  With colour on, each styled element of §8.2 carries its escape and the
+  columns still line up; `--no-color`, before or after a subcommand, and
+  `NO_COLOR` each give output with no escape byte.
 - **Parity check before release:** run `krino -n` beside the prototype's
   dry run over the same real directory, and explain every difference. The
   rules and the results stay outside the repository.