refactor: apply OOP design principles to core design

[Copilot]

Applies SRP, DRY, and Delegation principles to reduce cognitive load in three high-traffic areas: Castle.create(), Session, and agent_loop().

Changes

Castle.create() — SRP decomposition (castle.py)

A 70-line monolithic factory handling dirs, skill discovery, provider setup, channels, and session/model wiring. Extracted three focused private helpers:

cls._ensure_dirs(config)
skill_manager = cls._build_skill_manager(config)
channels = cls._build_channels(config, session_id=..., continue_latest=..., daemon=...)

create() is now a readable orchestrator; each helper carries a single responsibility.

Session.create() / Session.resume() — DRY fix (session/session.py)

Both classmethods ended with identical code: calling agent_factory(trace) and constructing Session. Extracted into _assemble():

return cls._assemble(session_dir=session_dir, meta=meta,
                     trace=trace, trace_manager=trace_manager,
                     agent_factory=agent_factory)

agent_loop() — trace recording extraction (kagent/loop.py)

The TurnEnd handler mixed hook dispatch, trace appending, and usage accumulation. Extracted _record_turn_end(state, event, *, run_id, turn_index) -> TokenUsage | None to own the trace concern, keeping the loop focused on orchestration.

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[Copilot]

Pull request overview

This PR refactors three frequently used orchestration paths to better separate responsibilities and remove duplicated assembly logic, improving readability without changing expected behavior.

Changes:

• Refactors Castle.create() into a small orchestrator by extracting directory creation, skill manager construction, and channel construction helpers.
• Removes duplicated Session.create() / Session.resume() wiring by extracting shared construction into Session._assemble().
• Extracts trace-recording from agent_loop() into _record_turn_end() to keep the main loop focused on control flow and hooks.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
packages/kcastle/src/kcastle/session/session.py	Introduces Session._assemble() to DRY up session construction in create() and resume().
packages/kcastle/src/kcastle/castle.py	Decomposes Castle.create() into _ensure_dirs, _build_skill_manager, and _build_channels helpers.
packages/kagent/src/kagent/loop.py	Extracts per-turn trace appends and usage extraction into _record_turn_end() and simplifies usage accumulation.

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