docs: update CLAUDE.md and ADR cross-references after Python orchestration migration

[mvillmow]

Parent epic: HomericIntelligence/Odysseus#143 — Move Python orchestration layer from Keystone to ProjectAgamemnon

Objective

Update CLAUDE.md and the ADR record in Keystone to reflect that the Python orchestration layer has been moved to ProjectAgamemnon, closing the loop on ADR-006/ADR-015.

Changes required

CLAUDE.md — "What Was Moved to ProjectAgamemnon (ADR-006)" section

Add the following paragraph after the existing list of extracted C++ components:

### Python orchestration layer (ADR-NNN, 2026)

The following Python modules were also extracted from Keystone into ProjectAgamemnon
as part of the ADR-006/ADR-015 follow-up (HomericIntelligence/Odysseus#143):

- `dag_walker.py` — DAGWalker (task ready-set computation, cycle detection)
- `task_claimer.py` — TaskClaimer (per-team concurrency guard, drain)
- `nats_listener.py` — NATSListener (NATS subject subscriber, `hi.tasks.>`)
- `maestro_client.py` — MaestroClient (AI Maestro REST client)
- `models.py` — Task, Agent, TaskEvent domain models
- `daemon.py` — orchestration daemon entry point
- `config.py`, `logging.py`, `validation.py` — supporting utilities

These modules are now part of `agamemnon.orchestration` in ProjectAgamemnon.
Keystone retains sole ownership of the NATS subject schema but no longer runs
a Python subscriber.

CLAUDE.md footer

Bump version from 2.0 to 3.0 and update the "Last Updated" date.

ADR

Either:

• Amend docs/adr/ADR-006-*.md to add a "Python follow-up (2026)" section, or
• Create docs/adr/ADR-NNN-python-orchestration-migration.md referencing ADR-006.

The ADR should record: what moved, why (CLAUDE.md mandate), when (Odysseus#143), and where (agamemnon.orchestration).

Depends on

N6 (HomericIntelligence/ProjectKeystone — deletion issue) must be merged first, or this can land together in the same PR.

Definition of done

• CLAUDE.md "What Was Moved" section lists all 10 migrated Python modules
• CLAUDE.md footer shows version 3.0 and current date
• An ADR entry documents the Python extraction decision and outcome