Design configurable pressure-driven consolidation policies

[TerminallyLazy]

Context

Raised by bio1-aws in Shiyao-Huang/awesome-agent-evolution#18: Tree Ring currently offers deterministic consolidation, but an embedding harness cannot express a fixed-capacity or pressure-triggered memory policy as a first-class Tree Ring contract.

Source discussion: Shiyao-Huang/awesome-agent-evolution#18 (comment)

Current behavior

• Consolidation runs only when a caller invokes tree-ring consolidate; Tree Ring does not run a daemon or autonomously schedule it.
• --period-type supports daily, weekly, monthly, yearly, and manual buckets.
• Project, agent-profile, workflow, and session filters partition the plan.
• Eligibility currently uses a fixed salience threshold plus protected ring/retention cases.
• Daily/manual summaries normally land in outer; weekly/monthly/yearly summaries normally land in inner; scar, seed, and sufficiently confident heartwood are preserved.
• Source memories remain intact, and the same period/source set is idempotent.
• There is no size-, count-, or byte-pressure trigger and no configurable metabolic-rate policy.

Desired design

Add an explicit, inspectable policy/planner surface that lets a harness decide when consolidation pressure is high enough without turning Tree Ring into a hidden autonomous scheduler. Candidate inputs may include:

• active memory count or approximate storage bytes by partition/ring;
• age/time window;
• event count since the last consolidation;
• configurable salience/retention eligibility;
• target output ring and maximum summary fan-in.

Acceptance criteria

• A read-only command/API reports pressure, selected sources, and the reason a threshold fired.
• Applying a plan remains explicit, deterministic, partition-aware, sensitivity-safe, and idempotent.
• Existing period-based behavior stays backward compatible.
• No background daemon or implicit mutation is introduced.
• Tests cover episodic/high-churn and semantic/low-churn profiles plus dry-run non-mutation.
• Documentation explains how a host can invoke the planner on an L1/backpack overflow event.