chore(scaffold): add solution skeleton for App, Ui, Data, Worker and tests

Create .slnx with five projects, wire references (App->Ui->Data,
Worker->Data, Tests->Worker+Data), install Avalonia/MVVM/SignalR.Client/
Sqlite/Hosting packages, and add schema.sql per docs/plan.md.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

schema/schema.sql

@@ -0,0 +1,62 @@
+-- ClaudeDo SQLite schema (single source of truth, 3NF)
+-- Applied by Worker on first startup. WAL mode is set via PRAGMA after open.
+
+PRAGMA foreign_keys = ON;
+
+CREATE TABLE IF NOT EXISTS lists (
+    id                  TEXT PRIMARY KEY,
+    name                TEXT NOT NULL,
+    created_at          TIMESTAMP NOT NULL,
+    working_dir         TEXT NULL,
+    default_commit_type TEXT NOT NULL DEFAULT 'chore'
+);
+
+CREATE TABLE IF NOT EXISTS tasks (
+    id            TEXT PRIMARY KEY,
+    list_id       TEXT NOT NULL REFERENCES lists(id) ON DELETE CASCADE,
+    title         TEXT NOT NULL,
+    description   TEXT NULL,
+    status        TEXT NOT NULL CHECK (status IN ('manual','queued','running','done','failed')),
+    scheduled_for TIMESTAMP NULL,
+    result        TEXT NULL,
+    log_path      TEXT NULL,
+    created_at    TIMESTAMP NOT NULL,
+    started_at    TIMESTAMP NULL,
+    finished_at   TIMESTAMP NULL,
+    commit_type   TEXT NOT NULL DEFAULT 'chore'
+);
+
+CREATE INDEX IF NOT EXISTS idx_tasks_list_id ON tasks(list_id);
+CREATE INDEX IF NOT EXISTS idx_tasks_status  ON tasks(status);
+
+CREATE TABLE IF NOT EXISTS tags (
+    id   INTEGER PRIMARY KEY AUTOINCREMENT,
+    name TEXT NOT NULL UNIQUE
+);
+
+CREATE TABLE IF NOT EXISTS list_tags (
+    list_id TEXT    NOT NULL REFERENCES lists(id) ON DELETE CASCADE,
+    tag_id  INTEGER NOT NULL REFERENCES tags(id)  ON DELETE CASCADE,
+    PRIMARY KEY (list_id, tag_id)
+);
+
+CREATE TABLE IF NOT EXISTS task_tags (
+    task_id TEXT    NOT NULL REFERENCES tasks(id) ON DELETE CASCADE,
+    tag_id  INTEGER NOT NULL REFERENCES tags(id)  ON DELETE CASCADE,
+    PRIMARY KEY (task_id, tag_id)
+);
+
+CREATE TABLE IF NOT EXISTS worktrees (
+    task_id     TEXT PRIMARY KEY REFERENCES tasks(id) ON DELETE CASCADE,
+    path        TEXT NOT NULL,
+    branch_name TEXT NOT NULL,
+    base_commit TEXT NOT NULL,
+    head_commit TEXT NULL,
+    diff_stat   TEXT NULL,
+    state       TEXT NOT NULL DEFAULT 'active' CHECK (state IN ('active','merged','discarded','kept')),
+    created_at  TIMESTAMP NOT NULL
+);
+
+-- Seed: minimal tag set (ignored if already present)
+INSERT OR IGNORE INTO tags (name) VALUES ('agent');
+INSERT OR IGNORE INTO tags (name) VALUES ('manual');