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>

.gitignore

@@ -0,0 +1,38 @@
+# Rust
+/target
+**/*.rs.bk
+Cargo.lock.bak
+
+# IDE
+/.idea
+/.vscode
+*.swp
+*.swo
+.DS_Store
+
+# Env / secrets
+.env
+.env.*
+!.env.example
+
+# Local config overrides
+config.local.toml
+/data
+/postgres-data
+
+# Dashboard
+/dashboard/node_modules
+/dashboard/.svelte-kit
+/dashboard/build
+/dashboard/.env
+
+# Caddy
+/caddy/data
+/caddy/config
+
+# Logs
+*.log
+/logs
+
+# OS
+Thumbs.db