feat(e2b): builds and built templates reach the network through their source pool's proxy

[CMGS]

What

Builds and built templates reach the network through the guarded egress proxy of their source pool, and a pool-image create's processes use that proxy too. This needs sandboxd cocoonstack/sandbox@dcffdec or later: a promoted template's clone takes its source pool's policy, and the claim reports net_route and accepts egress: false.

General packages (no e2b concept):

• pkg/sandboxd: ClaimSpec.Egress *bool and ClaimResult.NetRoute, plus NetRouteRelay.
• pkg/scale: ClaimOptions.NoEgress and Assignment.NetRoute, so the route reaches the caller and the opt-out reaches the node.

e2b

• envd builds a child's environment only from its /init defaults and the request. It never reads its unit's environment (e2b-dev/infra packages/envd/internal/services/process/handler/handler.go). So when a claim reports relay, this surface hands envd the variables silkd's unit sets: http_proxy and https_proxy http://127.0.0.1:3128, no_proxy localhost,127.0.0.1,::1,169.254.169.254. It hands them to envd at three points:
  • Build: a build seeds its step state with them, so every RUN step (root ones included) goes through the proxy. The final tokenless /init stores them as the template's defaults. An ENV step can override them.
  • Pool-image create: the /init carries them under the request's own envVars, so a caller's value wins.
  • Built-template create: it keeps them through the template defaults and the existing GET /envs merge.
  • A direct or none route sets nothing.
• allow_internet_access: false now claims any create with egress: false, a built template's or a pool image's. true or unset claims as before (true still picks the egress lane for a pool image). A built template no longer answers 400 for true.
• Docs: e2b-compat.md's no-network paragraph is replaced by "Network for builds":
  • how the proxy reaches builds and clones;
  • a worked config block that allow-lists the package indexes on the e2b-rt/e2b-ci pools;
  • that a template built before its pool gained a policy must be rebuilt;
  • that sudo steps drop the variables, so package installs run as root;
  • a pointer to sandboxd's egress rules for the tenant behavior change A1 made.

Kit rows

Two-node kit, sandboxd dcffdec on both hosts. The e2b-rt and e2b-ci none pools were given the package-index allow-list from the docs. Curl runs inside the guest through envd's commands.run.

row	kube	mesh
A2-01 pool-image create (e2b-rt): pypi.org / example.com, https_proxy in the process env	200 / 000 403, set	200 / 000 403, set
A2-02 Template.build from e2b-ci with RUN /opt/python/bin/pip install pyjokes (not in the image)	Successfully installed pyjokes-0.8.3, 4.0 s	same, 3.6 s
A2-03 the built template's sandbox: import pyjokes + requests.get(pypi), curl allowed / denied	pyjokes 200, 200 / 000 403	same
A2-04 built template with allow_internet_access=false	000 000 both (no proxy behind the relay)	same
A2-05 pool image with allow_internet_access=false	000 000 both, no proxy variables	same

Unchanged on this head:

• the D1, D2, D3a, D3b and D3c lanes, kube and mesh (S3 store included);
• B1 (single claim p50 1.13 ms), B2, E2-PY and the mesh rows;
• kube with the e2b API off (plain-42).

Hot path

A pool-image create on a relay route adds one small map clone (three entries plus the request's) before the /init it already makes. Any other route adds nothing.

Create→201 A/B, a6a86a5 (d3c) against this PR (a2), interleaved with the order swapped, p50 of 15 creates each:

run	front	a6a86a5 ms	this PR ms
1	kube	6.39 / 6.45 / 5.78 / 5.86	5.70 / 6.38 / 7.07 / 5.57
1	mesh	6.52 / 6.05 / 6.63 / 6.31	6.38 / 5.70 / 7.18 / 6.01
2	kube	7.52 / 6.11 / 5.78 / 6.47	5.84 / 5.77 / 5.63 / 5.85
2	mesh	6.53 / 7.17 / 6.27 / 5.47	6.05 / 8.11 / 6.52 / 5.79

No shift.

Tests

• TestStoreClaim_RoutesToAWarmNode: the route rides the assignment back, and NoEgress sends egress: false.
• TestARelayedBuildSeedsItsStepsWithTheProxyEnvironment: relay seeds both the RUN env and the /init defaults; none seeds neither.
• TestARelayedCreateHandsEnvdTheProxyUnderTheRequestEnvs: relay, none and direct; a request's no_proxy wins; allow_internet_access=false sets the opt-out on a pool image.
• TestARelayedBuildLeavesTheProxyInTheTemplateDefaults.
• TestACreateNamingABuiltTemplateClaimsItsKey: true is a plain claim, false is the opt-out.

Gates: lint 8× "0 issues.", fmt-check, asl -forwarder=false on both GOOS, tidy, tagged vet, race over all packages, helm lint.

Size

• Production Go: +43 / −9.
• Tests: +75 / −7.
• Comment lines: +7 / −1, all godoc on the new fields and one-line notes on the relay variables.