Myco v0.5.2 — Editable-by-default install model

TL;DR: the "Stable kernel, mutable substrate" framing inherited from v0.4.1 was wrong — it locked the kernel out of 永恒进化 + 永恒迭代 (L0 principles 3 and 4) because the agent can't edit code it imports from read-only site-packages. v0.5.2 makes editable install the primary documented path and ships a one-line bootstrap so the model works for new users.

Primary install path (new)

One line, no git ceremony:

pipx run --spec 'myco[mcp]' myco-install fresh ~/myco

Or two steps:

pip install 'myco[mcp]'
myco-install fresh ~/myco           # --dry-run to preview

That clones this repo to ~/myco, pip install -es it into the current Python environment, verifies via python -m myco --help, and optionally configures MCP hosts (--configure claude-code cursor windsurf …) in the same step.

Upgrade later with git pull inside ~/myco, not pip install --upgrade:

cd ~/myco && git pull && myco immune

What changed

New

• myco-install fresh [TARGET] — clone + editable install + optional host config in one command. Flags: --repo, --branch, --depth, --extras, --configure <clients…>, --force, --dry-run, --yes.
• myco-install host <client> — explicit subcommand for per-host MCP config. Legacy myco-install <client> still works.

Changed

• Trilingual READMEs rewritten (en/zh/ja): Stable kernel, mutable substrate → Editable by default. The kernel IS substrate. Quick Start leads with fresh. New Non-evolving install subsection documents plain pip install as the library-consumer path.
• docs/INSTALL.md restructured: new section 0 with the fresh flow; existing per-host matrix moved to section 1 with canonical myco-install host <client> form.
• src/myco/install/ restructured to argparse subparsers.

Non-breaking

• _canon.yaml emitted by v0.5.1 parses unchanged.
• Legacy myco-install cursor CLI still works (auto-routed to host cursor).
• All 16 verbs unchanged, all 9 lint dimensions unchanged.

Why this matters

Myco's L0 principles are uncompromising:

• 只为 Agent (principle 1): the agent IS the author, not a consumer.
• 永恒进化 (principle 3): the substrate's shape is mutable.
• 永恒迭代 (principle 4): iteration is continuous, not release-gated.

A read-only pip install freezes the kernel at release state, turning the agent into a consumer of code someone else wrote. The v0.5 scaffold verb — which writes to src/myco/<subsystem>/<verb>.py — was architecturally half-broken in a normal install because that path was read-only. fresh makes scaffold actually work end-to-end for the first time outside Myco's own dev checkout.

Doctrine records

• Three-round craft: docs/primordia/v0_5_2_editable_default_craft_2026-04-17.md
• Contract change: docs/contract_changelog.md v0.5.2 section
• Full CHANGELOG entry in CHANGELOG.md

Tests: 479 passed (was 465; +11 fresh tests, +3 subparser/legacy-sniff tests).