feat(cli): --features strict-network — stack presets instead of the wildcard

[shejnowicz]

Stacked on #105 (network presets) — the base branch is feat/2-network-presets; retarget to master after #105 merges. Follow-up to #2; no separate issue, so no close keyword.

Summary

sandcat init --features strict-network (or SANDCAT_STRICT_NETWORK=true) generates project settings whose network list holds one {"preset": "<stack>"} entry per resolved stack and no allow-all-GET wildcard. Everything beyond the stack registries and the user-settings layer (the agent's own API hosts) is then denied by default — including DNS resolution, so blocked hosts never even resolve.

• Opt-in by design: flipping the default would surprise every new project with "sandcat blocks the internet". The init summary states which policy the project got (Network: strict — stack presets: python, java vs default (allow all GET; tighten with --features strict-network)).
• init settings grows --strict-network / --stacks flags; with no stacks the strict list is empty (user-settings layer only).
• Only preset names land in the project file — the addon expands them at proxy start, so domain lists update with the sandcat version instead of freezing per project.
• scala resolves to java scala via the existing stack-deps mechanism, so both presets are seeded.

Test plan

• bats: init 167/167 (new: feature parsing incl. error-message listing, strict/default summary lines, settings --strict-network seeding, empty-stacks case, unknown-option rejection; interactive stubs updated for the new feature label)
• Full bats: 16/16 suites
• Hands-on integration in a real container: init --stacks python --features strict-network generates {\"network\":[{\"preset\":\"python\"}]} (no wildcard); stack healthy; pypi.org 200 (stack preset), www.anthropic.com + github.com 200 (presets expanded from the user-settings layer — expansion works across layers), example.com DNS REFUSED (rc=6 before HTTP); real PyPI package fetch end-to-end through the proxy (JSON API → wheel from files.pythonhosted.org, valid zip). Note: pip download itself is unavailable in the devbox/nix python (no ensurepip) — toolchain quirk, not policy; the fetch above covers the network path.

🤖 Generated with Claude Code

[adamw]

I guess the predefined network settings should hold as many presets, as stacks have been chosen? so each stack chosen (to install dependencies) translates to a network preset?

[shejnowicz]

Exactly — that's what this PR does: with --features strict-network, every resolved stack becomes one {"preset": ""} entry in the project settings (so --stacks python,java → presets python + java; scala resolves to java scala via the existing stack-deps mechanism and gets both). A test keeps STACK_NAMES and the preset registry in sync so a new stack can't ship without a matching preset.

[adamw]

Ah ok, thanks :)