fix(composer): handle ANSI ghost text safely

[kunchenguid]

Intent

Fix a fleet-critical bug: away-mode escalation injection wedged all night on the primary claude-on-herdr pane because the composer classifier false-read de-emphasised ghost/placeholder text as real pending input (6524 defers; empirically reproduced read-only from the live primary pane - claude's rotating prompt-suggestion ghost is a bare '❯' then SGR-2 dim text, which herdr's ANSI pane read preserves; the tmux path already stripped dim but the herdr path only had a narrow codex bold-wrapped byte-pattern check that claude's non-bold prompt never matched).

Per explicit captain direction, consolidate ghost-text stripping into ONE ANSI-aware classification owner that both ANSI-capable backends route through, instead of per-harness one-offs. Key decisions and deliberate tradeoffs a diff reader would not know:

• fm_composer_strip_ghost (bin/fm-composer-lib.sh) is the single owner. It drops every de-emphasised run: SGR-2 dim/faint (claude/codex) AND a dark/muted TRUECOLOR foreground (grok's placeholder) whose perceived luminance is below FM_COMPOSER_GHOST_LUMA_MAX (default 128, new tunable). This closes the previously-documented grok TRUECOLOR gap by the SAME mechanism, per acceptance criteria.
• The dark-truecolor rule deliberately assumes a dark terminal theme (the fleet reality; empirically grok real input is bright 38;2;224;222;244 lum ~225 kept, muted UI is 38;2;50;47;70..110;106;134 lum ~51..110 dropped). SGR-2 stays theme-independent. Bias is conservative: under-stripping merely defers (surfaced by the max-defer alarm), so 256-color (38;5) is deliberately NOT luminance-tested (palette-dependent, not empirically needed) and only truecolor 38;2 is.
• fm_tmux_strip_ghost and fm_backend_herdr_strip_ansi are reduced to thin adapters over the shared owner; the herdr-only faint byte-pattern check (fm_backend_herdr_prompt_tail_is_faint) is removed because the generic dim strip subsumes it (codex faint regressions stay green through the shared path).
• Bordered-composer detection now reads the PLAIN row (not the ghost-stripped one) because in a dark theme the box border is itself dark truecolor and drops with the ghost; reading shape from the plain row keeps that correct.
• Two pre-existing ghost-test fixtures that used a near-black 38;2;1;2;3 as 'real' colored text were intentionally corrected to a bright 38;2;224;222;244: near-black was never a realistic real-input color (invisible on a dark bg) and only existed to exercise the truecolor payload-skip parser, which the bright value still exercises. This is a deliberate fixture correction, not a weakened assertion.
• Scope was deliberately kept to the composer classification layer only (fm-composer-lib.sh, fm-tmux-lib.sh, backends/herdr.sh) and did NOT touch fm-supervise-daemon.sh / fm-watch.sh / fm-classify-lib.sh, to avoid conflict with a concurrently-landing paused-state supervision PR (feat(watcher): add paused external-wait supervision #421).
• The observed 'wedge alarm alarmed into the void' secondary concern (inject_wedge_alarm only actively signals via the tmux status line, skipped on herdr) is deliberately deferred to its own filed task (fm-wedge-alarm-oob-w3), not in this diff.
  Evidence and the incident write-up (exact ANSI bytes, dates, versions, commands) are in docs/herdr-backend.md; deterministic regressions feed the exact captured bytes through the real classifiers (tests/fm-backend-herdr.test.sh, tests/fm-composer-ghost.test.sh); the harness-adapters skill's grok gap note and docs/configuration.md are updated.

What Changed

• Centralized ANSI ghost extraction in fm-composer-lib.sh so tmux and Herdr ignore dim/faint suggestions and dark truecolor placeholders while retaining real typed input.
• Kept composer-shape detection separate from ghost stripping and classify erased unbordered shell prompts as unknown, preventing away-mode injection into an exited shell.
• Added regressions for dim ghosts, Grok truecolor placeholders, and dark shell prompts, and updated AFK, backend, configuration, and harness guidance.

Risk Assessment

⚠️ Medium: Captain, the change is internally consistent but modifies a safety-critical ANSI-based injection guard shared by two backends.

Testing

The supplied baseline full suite had passed. Focused classifier regressions and a controlled end-to-end ANSI transcript confirm SGR-2 and dark truecolor ghost text classify as empty on tmux and Herdr, while bright bordered input remains pending; the transcript also verifies the configured luminance threshold behavior.

Evidence: ANSI composer classifier end-to-end transcript

shared/default-luma-128 dark-placeholder-output=<❯ > expected=<❯ >
shared/luma-50 dark-placeholder-output=<❯ Type a message...> expected=<❯ Type a message...>
tmux/claude_dim_ghost cursor_row=0 captured_ansi=\342\235\257 \033[2mwhat did the wheelhouse verification fi\|nd?\033[0m$| verdict=empty expected=empty
tmux/grok_dark_bordered_placeholder cursor_row=0 captured_ansi=\033[38;2;86;82;110m\342\224\202\033[38;2;224;222;244m \342\|\235\257 \033[38;2;50;47;70mType a message...\033[38;2;86;8\|2;110m \342\224\202\033[39m$| verdict=empty expected=empty
tmux/grok_bright_bordered_input cursor_row=0 captured_ansi=\033[38;2;86;82;110m\342\224\202\033[38;2;224;222;244m \342\|\235\257 land the queued patch \033[38;2;86;82;110m\342\224\|\202\033[39m$| verdict=pending expected=pending
herdr/claude_dim_ghost capture=controlled-ansi-fixture verdict=empty expected=empty
herdr/grok_dark_bordered_placeholder capture=controlled-ansi-fixture verdict=empty expected=empty
herdr/grok_bright_bordered_input capture=controlled-ansi-fixture verdict=pending expected=pending
cleanup=all temporary tmux sessions removed

Pipeline

Updates from git push no-mistakes

✅ **intent** - passed

✅ No issues found.

🔧 **Rebase** - 1 issue found → auto-fixed ✅

• ⚠️ docs/herdr-backend.md - merge conflict rebasing onto origin/main

🔧 Fix applied.
✅ Re-checked - no issues remain.

🔧 **Review** - 1 issue found → auto-fixed (2) ✅

• 🚨 bin/fm-tmux-lib.sh:101 - Captain, a dark truecolor dead-shell prompt such as $ is stripped before classification, turning the safety result from unknown into empty. AFK escalation may then type and submit into an exited shell. Preserve or re-check unbordered shell-prompt shape from the plain row before classifying stripped content.

🔧 Fix: Preserve dark shell prompt safety
1 error still open:

• 🚨 bin/fm-composer-lib.sh:185 - Captain, the new safety backstop recognizes only an exact plain $, >, %, or #. A dead tmux shell prompt such as user@host $ rendered entirely in a dark truecolor is stripped to empty, does not match this check, and then falls through as empty; away-mode can inject and execute its digest in that exited shell. Preserve unknown for any nonempty unbordered plain row that ghost stripping erased, except verified agent-composer shapes.

🔧 Fix: Harden erased shell prompt classification
✅ Re-checked - no issues remain.

✅ **Test** - passed

✅ No issues found.

• command -v tmux >/dev/null || { echo "tmux is required for e2e tests" >&2; exit 1; }; tmux -V; rc=0; for t in tests/*.test.sh; do echo "== $t =="; bash "$t" || rc=1; done; exit "$rc"
• Baseline previously successful: command -v tmux >/dev/null || { echo "tmux is required for e2e tests" >&2; exit 1; }; tmux -V; rc=0; for t in tests/*.test.sh; do echo "== $t =="; bash "$t" || rc=1; done; exit "$rc"
• bash tests/fm-composer-lib.test.sh
• bash tests/fm-composer-ghost.test.sh
• bash tests/fm-backend-herdr.test.sh
• Controlled ANSI fixture harness through production tmux capture and Herdr classifier entry points, recorded in composer-ansi-e2e-transcript.txt.

✅ **Document** - passed

✅ No issues found.

✅ **Lint** - passed

✅ No issues found.

✅ **Push** - passed

✅ No issues found.