fix(keepopen): honour NO_COLOR and auto-strip ANSI for non-TTY stdout (#176)

## Summary

`keepopen.sh` always emitted ANSI colour escapes — even when the user
redirected output to a file or pipeline, and even when `NO_COLOR=1`
was set. [no-color.org](https://no-color.org/) has been the canonical
opt-out env var since 2017; respecting it is one of the cheapest UX
wins available.

## Change

At the top of `keepopen.sh`, if either `NO_COLOR` is set OR stdout is
not a TTY, all colour variables become empty strings. Banners and
prefix labels become plain text — still loud and clearly labelled,
just without escapes.

\`\`\`bash
if [[ -n "${NO_COLOR:-}" ]] || [[ ! -t 1 ]]; then
    C_RED='' C_YEL='' C_CYA='' C_GRN='' C_BOLD='' C_RST=''
else
    # original ANSI definitions
fi
\`\`\`

## Verified

\`\`\`
$ NO_COLOR=1 keepopen.sh testapp /tmp false false | grep -c $'\033'
0
$ keepopen.sh testapp /tmp false false | grep -c $'\033' # piped → not
TTY
0
\`\`\`

Desktop-launch path keeps colour (real terminal, no `NO_COLOR`), so
the on-screen failure banners are unchanged. The new behaviour only
fires when:

- User has `NO_COLOR` set globally (their explicit preference), or
- Output is piped to a file / capture (CI logs, `tee`, `.log`
  redirects)

## Scope

Touches `launcher/keepopen.sh` only — not part of the
a2ml↔adoc lock-step group, so the gate in #172 does not fire on this
PR.

## Coordination

Independent of all other open launcher-standard PRs (#170, #171,
#172, #173, #175) — different file, no conflicts in any merge order.

## Test plan

- [x] `NO_COLOR=1` produces zero ANSI escapes
- [x] Pipe (non-TTY stdout) produces zero ANSI escapes
- [x] Default TTY behaviour unchanged (loud red/yellow banners)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

launcher/keepopen.sh

@@ -38,12 +38,21 @@ GUI_CMD="${3:?keepopen: GUI_CMD required (arg 3) — pass '' if not applicable}"
 TUI_CMD="${4:?keepopen: TUI_CMD required (arg 4) — pass '' if not applicable}"
 LOG_FILE="${5:-}"
 
-C_RED=$'\033[1;31m'
-C_YEL=$'\033[1;33m'
-C_CYA=$'\033[1;36m'
-C_GRN=$'\033[1;32m'
-C_BOLD=$'\033[1m'
-C_RST=$'\033[0m'
+# Honour NO_COLOR (https://no-color.org/) and auto-detect non-TTY stdout.
+# When set, banners and prefix labels emit no ANSI escapes — still loud
+# and clearly labelled, just plain text. The freedesktop-style desktop
+# launch redirects stdout to a real terminal so this rarely triggers
+# automatically, but covers `keepopen.sh ... | tee` and CI captures.
+if [[ -n "${NO_COLOR:-}" ]] || [[ ! -t 1 ]]; then
+    C_RED='' C_YEL='' C_CYA='' C_GRN='' C_BOLD='' C_RST=''
+else
+    C_RED=$'\033[1;31m'
+    C_YEL=$'\033[1;33m'
+    C_CYA=$'\033[1;36m'
+    C_GRN=$'\033[1;32m'
+    C_BOLD=$'\033[1m'
+    C_RST=$'\033[0m'
+fi
 
 banner() {
     # $1 = colour; $2 = title; remaining args = body lines.