feat: add stack targeting and shared build contexts

CHANGELOG.md

@@ -7,6 +7,29 @@ and this project follows [Semantic Versioning](https://semver.org/).
 
 ## [Unreleased]
 
+### Added
+
+- Add persistent integer stack IDs and `<stack>.<container>` container IDs, shown
+  in a new `ID` column in `wco ps` and `wco stacks` and in their JSON output. Stack
+  1 is always the shared project; isolated worktrees are numbered from 2 and keep
+  their ID, recorded in `ports.json`, until the worktree is removed.
+- Accept an ID directly after a Docker Compose command to target another stack, or
+  a single container inside it, without changing directory — `wco down 2`,
+  `wco --isolated down 2`, `wco restart 2.1`, `wco logs 2.1 -f`, `wco exec 2.1 sh`.
+  A container ID resolves to its Compose service name; `down` acts on whole stacks
+  and rejects one.
+
+### Changed
+
+- Bump the `ports.json` state format to version 2, adding recorded stack IDs.
+  Version 1 files are read and upgraded in place on the next write.
+
+### Fixed
+
+- Resolve missing worktree-relative build contexts from the central WCO workspace when the same
+  path exists there, while preserving active-worktree resolution for bind mounts and build
+  contexts that are present in the checkout.
+
 ## [1.2.1] - 2026-08-03
 
 ### Changed

README.md

@@ -90,6 +90,9 @@ Things worth knowing:
 - Initialization never changes the Compose file.
 - Relative Compose paths such as `./` resolve from the **active worktree**, and Docker Compose
   loads `.env` from that worktree for interpolation.
+- If a relative build context is absent from the active worktree but the same path exists beside
+  `.wco.toml`, WCO uses that central workspace path. This supports shared Dockerfiles such as
+  `build: { context: ./docker/nginx }` without changing worktree-relative bind mounts.
 - Declare parameterized published ports under `[isolation.ports]`.
 - Existing `.wco.toml` files are not replaced unless `--force` is supplied.
 
@@ -105,7 +108,7 @@ wco down
 ```
 
 **Output.** Interactive commands use colored, terminal-aware output. `wco ps` presents a
-responsive `NAME`, `STATUS`, `WORKTREE`, and `BRANCH` table with status highlighting, and
+responsive `ID`, `NAME`, `STATUS`, `WORKTREE`, and `BRANCH` table with status highlighting, and
 supports Compose filters, service arguments, `--all`, `--status`, `--orphans`, and `--no-trunc`.
 When output is redirected — or when `--format`, `--quiet`, or `--services` is supplied — WCO
 delegates the output to Docker Compose unchanged. Set [`NO_COLOR`](https://no-color.org/) to
@@ -128,6 +131,26 @@ wco stacks --format json
 workspace's shared project or the isolated project derived from their recorded worktree, so
 stacks belonging to other projects are never listed.
 
+**Targeting a stack by ID.** Every row carries an `ID` of the form `<stack>.<container>`. Stack 1
+is always the shared project; isolated worktrees are numbered from 2 and keep their ID until the
+worktree is removed, so an ID is safe to script against. Pass one directly after a Compose command
+to act on that stack — or that single container — without changing directory:
+
+```bash
+wco down 2          # bring down stack 2, wherever you are
+wco restart 2.1     # restart just that container's service
+wco logs 2.1 -f     # ...the ID comes first, then the flags
+wco exec 2.1 sh
+```
+
+A container ID resolves to its Compose service name, so it works with any command that accepts
+services. `down` acts on whole stacks and rejects a container ID — use `stop` for one container.
+The ID is only read in the position immediately after the Compose command, which keeps numeric
+option values such as `wco logs --tail 20` untouched; the same rule means a service literally
+named `2` cannot be targeted this way. Stack IDs are recorded alongside port slots in `ports.json`
+(see [Port assignments and state](#port-assignments-and-state)) and are reused once the worktree
+they name is gone.
+
 **Where containers run.** The `WORKTREE` column reports the worktree each listed container was
 actually created from — not the one you are standing in — and is highlighted when the two differ.
 `BRANCH` shows that worktree's checked-out branch, or the short revision in parentheses when the
@@ -311,15 +334,18 @@ needed and remain available for later commands such as `wco --isolated down`.
 ### Port assignments and state
 
 The first isolated worktree receives each base port plus one `port_step`, the next receives the
-lowest available slot, and assignments remain stable in `ports.json`:
+lowest available slot, and assignments remain stable in `ports.json`. The same file records each
+worktree's stack ID, so both survive across invocations:
 
 | Platform | State file |
 | --- | --- |
 | Linux, macOS, WSL2 | `~/.local/state/wco/ports.json` (or `$XDG_STATE_HOME/wco/ports.json`) |
 | Native Windows | `%LOCALAPPDATA%\wco\ports.json` |
 
 Generated isolation overrides for container names and fixed ports use the adjacent `overrides/`
-directory.
+directory. Entries whose config file or worktree no longer exists are pruned on read, which frees
+both the port slot and the stack ID for reuse. WCO upgrades an older `ports.json` in place the
+first time it writes to it.
 
 > [!NOTE]
 > `wco` controls Docker Compose's project name, so `-p` and `--project-name` are intentionally