Session Notes' 10-entry trim can drop early loop-transition breadcrumbs on long tickets

[hpieris-dm]

Problem

append_session_note (src/dmx/loop_memory.py) keeps only the most recent _MAX_SESSION_NOTES = 10 entries in .dmx/activeContext.md's ## Session Notes section.

A ticket with a dev loop that iterates many times via repeat_until: all_phases_complete appends one "iterating (round N)" note per phase, plus one note per loop transition (spec complete → chained to plan, plan complete → chained to dev, etc). On a ticket with more than ~10 phases/transitions, the earliest breadcrumbs (e.g. "spec loop completed — chained to plan") scroll out of the window before the ticket finishes.

Purely cosmetic — activeContext.md Session Notes is a rolling human-readable log surfaced as context to the next skill, not a source of truth. The full history is still recoverable from the per-run state files under .dmx/jobs/{job_id}/. No functional/correctness impact, just a reduced narrative trail for a long-running ticket.

Proposal

• Bump _MAX_SESSION_NOTES (or make it configurable), and/or
• Trim by significance instead of pure recency — e.g. always keep the most recent note per loop name/transition rather than a flat last-N window.

Trivial, no external contract — _MAX_SESSION_NOTES is an internal implementation constant, not part of any public interface.