Split the POSIX CLI into modules

linux/claude-mode was 3,035 lines. It is now 177: the paths and flags, a
loader, and the command dispatch. Everything else moved, verbatim, into
twelve files under linux/lib/, one per concern - output, core, preflight,
sessions, switch, catalogue, commands, doctor, presets, menu, setup, repair.
The move was done by line range with a check that every original line landed
in exactly one file; the only thing that changed place is the switch's
running-sessions question, which now sits with session detection.

The CLI finds lib/, cm-json.py and cm-vault.sh beside itself, following the
~/.local/bin symlink, so a checkout runs its own code rather than the
installed version's (it used to mix the two). The key helper path written
into settings.json is still the installed one.

linux/install.sh ships bin/lib/, clearing old modules first so a removed one
cannot linger. The package build copies linux/ recursively, which a flat copy
would not.

tests/cli/test_install.sh runs the real installer into a sandbox home: every
file lands, the symlink runs, a reinstall keeps edited presets and drops a
stale module. docs/architecture.md lists the modules.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

linux/install.sh

@@ -72,6 +72,11 @@ install -m 0755 "$SRC/claude-mode"          "$ROOT/bin/claude-mode"
 install -m 0755 "$SRC/claude-key-helper.sh" "$ROOT/bin/claude-key-helper.sh"
 install -m 0644 "$SRC/cm-json.py"           "$ROOT/bin/cm-json.py"
 install -m 0644 "$SRC/cm-vault.sh"          "$ROOT/bin/cm-vault.sh"
+# The CLI is split across lib/*.sh, loaded from beside bin/claude-mode. Cleared
+# first, so a module removed from the source does not linger and get loaded.
+mkdir -p "$ROOT/bin/lib"
+rm -f "$ROOT/bin/lib/"*.sh
+for f in "$SRC"/lib/*.sh; do install -m 0644 "$f" "$ROOT/bin/lib/"; done
 green 'copied claude-mode + helpers'
 
 # cm_version() reads this; without it every health.json reported 0.0.0.