Fix #42228: Inherit parent session cwd in compressed continuation sessions

[Morad37]

Summary

During context compression, the continuation (tip) session row was created
without inheriting the parent session's working directory (cwd). This caused
compressed conversations to appear under "No workspace" in the TUI/desktop
session list, even when the root session had a recorded cwd.

Changes

hermes_state.py — Added get_session_cwd() method to SessionDB,
mirroring the existing get_session_title() pattern, so callers can
retrieve a session's recorded working directory.

agent/conversation_compression.py — In compress_context(), before
the session rotation, look up the old session's cwd from the database
and pass it to create_session() for the new continuation row.

Root Cause

create_session() accepts an optional cwd parameter, and the initial
session creation in run_agent.py does pass it (via
_launch_cwd_for_session). But the compression rotation path in
compress_context never copied the parent's cwd, so every continuation
session had cwd=NULL.

Testing

• All 8 TestCompressionChainProjection tests pass, including
  test_list_projection_uses_tip_cwd (which validates that a tip with
  a persisted cwd projects correctly onto the lineage row).
• All 24 test_413_compression tests pass.
• All 25 test_compression_feasibility + test_compression_persistence
  • test_compression_boundary_hook tests pass.
• All 16 compression lock + concurrent fork tests pass.
• No regressions in test_hermes_state or other session tests.

Fixes #42228

[teknium1]

Thanks for this — the diagnosis and fix are correct for the rotation path.

Context on why we're closing it: as of #52658 (#38763), compression.in_place now defaults to True. Compaction keeps ONE durable session id for the conversation's whole life — it no longer ends the session and forks a continuation id. Because there is no continuation session, the conversation keeps its original cwd through compaction — there is no null-cwd continuation row to inherit into.

Rotation now only runs as an explicit opt-out (compression.in_place: false), and the direction is to treat that path as legacy. So this fix hardens a code path that no longer executes by default and that we're not investing further in. Closing as superseded by the in-place default — not a reflection on the code, which was a correct fix for the behavior at the time. Credit preserved in the issue/PR history. Appreciate the contribution.