chore: initial scaffold — workspace, docs, blueprint

Sets up the PiCloud monorepo as a Cargo workspace organised around the
three-service architecture (manager / orchestrator / executor), each
backed by a *-core library crate so the same logic powers both the MVP
all-in-one `picloud` binary and the future split-process cluster mode.

  * crates/shared, executor-core, orchestrator-core, manager-core
    define the library surface and trait seams between the three
    services (`ExecutorClient`, `ScriptResolver`, `ScriptRepository`).
  * crates/picloud is the MVP entrypoint; serves /healthz on 8080
    (override via PICLOUD_BIND).
  * crates/picloud-{manager,orchestrator,executor} are skeleton
    binaries that keep the crate boundaries honest until cluster
    mode is built out in v1.3+.
  * docs/git-workflow.md defines the trunk-based workflow:
    short-lived branches, Conventional Commits, separate hotfix
    flow with mandatory reproduction tests.
  * CLAUDE.md captures the working rules for future Claude sessions.

Workspace passes `cargo fmt`, `cargo clippy -D warnings` (with
pedantic enabled), and `cargo test --workspace`. The all-in-one
binary responds on `/healthz` and `/`.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/manager-core/src/repo.rs

@@ -0,0 +1,83 @@
+use async_trait::async_trait;
+use picloud_orchestrator_core::{ResolverError, ScriptResolver};
+use picloud_shared::{Script, ScriptId};
+use sqlx::PgPool;
+
+#[derive(Debug, thiserror::Error)]
+pub enum ScriptRepositoryError {
+    #[error("database error: {0}")]
+    Db(#[from] sqlx::Error),
+
+    #[error("not found: {0}")]
+    NotFound(ScriptId),
+}
+
+/// CRUD over the `scripts` table.
+#[async_trait]
+pub trait ScriptRepository: Send + Sync {
+    async fn get(&self, id: ScriptId) -> Result<Option<Script>, ScriptRepositoryError>;
+    async fn list(&self) -> Result<Vec<Script>, ScriptRepositoryError>;
+    async fn create(&self, script: &Script) -> Result<(), ScriptRepositoryError>;
+    async fn update(&self, script: &Script) -> Result<(), ScriptRepositoryError>;
+    async fn delete(&self, id: ScriptId) -> Result<(), ScriptRepositoryError>;
+}
+
+pub struct PostgresScriptRepository {
+    pool: PgPool,
+}
+
+impl PostgresScriptRepository {
+    #[must_use]
+    pub fn new(pool: PgPool) -> Self {
+        Self { pool }
+    }
+}
+
+// Real query bodies land alongside the first migration. Stubbing the trait
+// impl so the workspace compiles and the seam is visible.
+#[async_trait]
+impl ScriptRepository for PostgresScriptRepository {
+    async fn get(&self, _id: ScriptId) -> Result<Option<Script>, ScriptRepositoryError> {
+        let _ = &self.pool;
+        Ok(None)
+    }
+
+    async fn list(&self) -> Result<Vec<Script>, ScriptRepositoryError> {
+        Ok(Vec::new())
+    }
+
+    async fn create(&self, _script: &Script) -> Result<(), ScriptRepositoryError> {
+        Ok(())
+    }
+
+    async fn update(&self, _script: &Script) -> Result<(), ScriptRepositoryError> {
+        Ok(())
+    }
+
+    async fn delete(&self, _id: ScriptId) -> Result<(), ScriptRepositoryError> {
+        Ok(())
+    }
+}
+
+/// Adapts a `ScriptRepository` into the `ScriptResolver` trait the
+/// orchestrator depends on, so we don't pull the manager into the
+/// orchestrator's dependency graph.
+pub struct RepoResolver<R: ScriptRepository> {
+    repo: R,
+}
+
+impl<R: ScriptRepository> RepoResolver<R> {
+    pub fn new(repo: R) -> Self {
+        Self { repo }
+    }
+}
+
+#[async_trait]
+impl<R: ScriptRepository> ScriptResolver for RepoResolver<R> {
+    async fn resolve(&self, id: ScriptId) -> Result<Option<Script>, ResolverError> {
+        self.repo
+            .get(id)
+            .await
+            .map_err(|e| ResolverError::Backend(e.to_string()))
+    }
+}