feat(project): container template, .env.local/.gitignore scaffolding, and project resolution

[tejaskash]

First PR for agentcore project dev. Before we can run anything locally, two things need to exist: a way to create a container-based project, and a way for commands to find the project they're running in. This PR does both.

What changed

Added a hello-world-python-container template. It's the same Strands agent as the existing template, just built as a container instead of a CodeZip. The Dockerfile is static on purpose — no handlebars conditionals like the old CLI had, since our asset pipeline is a plain byte copy.

New projects also get a root .gitignore and an agentcore/.env.local starter file. The dev command will load .env.local in a later PR. These render from *.template assets because npm strips dotfiles when publishing.

While copying the template I found that pyproject.toml points at a README.md we never shipped. That silently worked for CodeZip but breaks the container build (uv sync runs hatchling, hatchling errors on the missing readme). Both templates now ship a README.

FsProjectManager.resolve() is implemented: walk up from cwd looking for agentcore/agentcore.json, same as git looks for .git. The parsed spec is validated loosely, so projects from the current CLI that carry sections we don't read yet (memories, gateways) still resolve. Two failure modes are now distinct: no project found returns undefined (the middleware turns that into NoProjectError with a hint to run project create), while a broken config throws InvalidProjectConfigError with the zod details. The old CLI conflated these — a JSON typo showed up as "no project found".

withProject is now mounted on every project subcommand except create, so handlers just read the project off the context.

Testing

The main test is a round-trip: create a project from each template, resolve it from a nested subdirectory, and check the models match. Plus coverage for the miss/malformed/legacy cases. 554 tests pass.

What's next

This is 1 of 6 planned PRs for dev: dev server core + CodeZip runner, container runner, OTLP collector, the Agent Inspector web server, and finally the project dev handler that wires it together.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.01%. Comparing base (5849293) to head (3c9ec6c).

Additional details and impacted files

@@             Coverage Diff              @@
##           refactor    #1880      +/-   ##
============================================
+ Coverage     95.98%   96.01%   +0.03%     
============================================
  Files           208      208              
  Lines          9684     9764      +80     
============================================
+ Hits           9295     9375      +80     
  Misses          389      389              

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