cli: extract journal and misc commands, complete split

Move remaining extractable handlers into cli/journal.rs and cli/misc.rs.
Functions depending on main.rs helpers (cmd_journal_tail, cmd_journal_write,
cmd_load_context, cmd_cursor, cmd_daemon, cmd_digest, cmd_experience_mine,
cmd_apply_agent) remain in main.rs — next step is moving those helpers
to library code.

main.rs: 3130 → 1331 lines (57% reduction).
cli/ total: 1860 lines across 6 focused files.

Co-Authored-By: Kent Overstreet <kent.overstreet@linux.dev>

poc-memory/src/cli/mod.rs

@@ -7,3 +7,5 @@ pub mod graph;
 pub mod node;
 pub mod agent;
 pub mod admin;
+pub mod journal;
+pub mod misc;