feat: publish pure v3 plugin runtime

.github/workflows/plugin-api-v3.yml

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+name: plugin-api-v3
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  contract:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/checkout@v4
+        with:
+          repository: akashic-plugins/plugin-contracts
+          ref: 4dd69dd621e029e51e99aa428443fa3a4ec1f6cf
+          path: .plugin-contracts
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.13"
+      - name: Check Plugin API v3
+        env:
+          PYTHONPATH: .plugin-contracts
+        run: python -m akashic_plugin_contracts check plugin.py
+
+  composition-parity:
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/checkout@v4
+        with:
+          repository: kachofugetsu09/akashic-agent
+          ref: 3005f838bcd96e2cbc58616aede46e4f39df4523
+          path: .akashic-core
+      - uses: actions/setup-python@v5
+        with:
+          python-version: "3.13"
+          cache: pip
+          cache-dependency-path: .akashic-core/requirements.txt
+      - name: Install exact Core runtime
+        run: |
+          python -m venv .venv
+          .venv/bin/python -m pip install \
+            -r .akashic-core/requirements.txt \
+            -r .akashic-core/requirements-dev.txt \
+            pytest pytest-asyncio
+      - name: Verify Plugin Undo v3 composition
+        env:
+          AKASHIC_AGENT_ROOT: ${{ github.workspace }}/.akashic-core
+          PYTHONPATH: ${{ github.workspace }}/.akashic-core
+        run: cd tests && ../.venv/bin/python -m pytest -q .
+      - name: Check v3 source types
+        env:
+          PYTHONPATH: .akashic-core
+        run: .venv/bin/pyright --pythonpath .venv/bin/python --level error plugin.py
+      - name: Compile Python sources
+        run: python -m compileall -q .
+      - name: Check diff formatting
+        run: git diff --check

README.md

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+# Plugin Undo
+
+Plugin Undo 提供 `/undo`，撤销当前 Session 最后一个完整的 completed interaction。
+
+插件是 pure Plugin API v3，只声明 `COMMANDS` 与 `INTERACTION_UNDO`。SessionDB backup、
+interaction transcript/embedding 删除、Default Memory durable reconciliation 和 Akasha rebuild
+都由 Core `189c25a3e011c90cc8106fdda0b57c8c0ae71730` 拥有；插件不接触 SessionManager、SQL、
+memory engine 或正式 workspace。
+
+候选 generation 只验证拓扑与 command catalog，不能调用 destructive owner。正式 `/undo` 若
+Session 删除已提交但 Default Memory 尚待收敛，会明确返回 error 结果，Core 在当前进程 retry 或
+进程重启时重放 pending receipt。

akashic.plugin.toml

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+schema_version = 1
+name = "plugin_undo"
+version = "2.0.0"
+api_version = 3
+entrypoint = "plugin.py"