mpm compose up --watch: Docker build cache not invalidated on source changes

[firstdorsal]

Problem

mpm compose up --watch correctly detects source file changes in build context directories and re-triggers the deploy cycle, but Docker's build layer cache is not invalidated. The container keeps running with old code.

Root Cause

In utils/mows-cli/src/package_manager/compose/docker.rs, compose_up passes --build but never --no-cache:

cmd.arg("up");
if options.build {
    cmd.arg("--build");
}

--build alone relies on Docker's BuildKit layer cache. When COPY src src encounters the same content hash (stale cache), it skips rebuilding even though files changed.

Expected Behavior

When --watch detects changes in a build context directory, the subsequent rebuild should pick up the new source files.

Suggested Fix

When the watch detects a change in a build context directory (as extracted by extract_build_contexts), pass --no-cache for that specific service's rebuild. This avoids unnecessarily rebuilding all services while ensuring changed contexts are rebuilt fresh.

Alternatively, a simpler approach: always pass --no-cache during watch-triggered rebuilds (not on the initial deploy).

Reproduction

1. mpm compose up --watch on a project with a Rust API build context
2. Modify a source file in the build context
3. Watch triggers a re-deploy, but the container runs old code
4. docker compose build --no-cache api followed by mpm compose up correctly picks up changes