fix(proxy): exclude reserved path segments from Go container name extraction

[abienkowski]

Closes #24.

The divergence

/containers/<x> is ambiguous: <x> is usually a container name, but Docker also has reserved endpoints at that position — /containers/json lists, /containers/create creates. Rust (rs/src/proxy.rs:212) and TypeScript (ts/src/proxy.ts:125) already excluded create/json/exec. Go excluded nothing:

extractContainerName("/containers/json")   = "json"
extractContainerName("/containers/create") = "create"
extractContainerName("/containers/exec")  = "exec"

It was worse than the issue described

#24 said Go returned Allow where Rust/TS returned Deny, and flagged that this was diffed rather than tested. Testing it showed the practical effect is sharper: Allow here means the request is actually forwarded to the Docker daemon.

Reverting the fix and running the integration suite:

FAIL: DELETE /containers/json -> 403 (reserved, not a container) (expected 403, got 404)

That 404 comes from Docker, not from the proxy — Go proxied a DELETE through to the daemon that Rust and TypeScript refused to forward at all. It happens to be harmless because no container is named json, but the request reached the daemon.

Path: reserved word taken as a container name → lifecycle branch → routeByContainerName → unknown container → ActionAllow.

The fix

Go now excludes the same three segments, with a comment pointing at the Rust and TypeScript equivalents so the three stay linked.

GET /containers/json is unaffected: with the reserved word excluded it falls through to the GET/HEAD passthrough, so listing still works. That is asserted in all three languages and in the integration suite.

Tests

Counts against current main (05320aa), re-measured after rebasing onto it on 2026-10-02:

	before	after
Go	97	99
Rust	135	137
TypeScript	154 (1 skipped)	155 (1 skipped) — proxy suite 26 → 27
integration	27 ×3	30 ×3

After the rebase, make test-all and make lint-all pass, and all three integration suites (make test-integration{,-rs,-ts}) pass 30/30, including the three new reserved-segment checks. AGENTS.md's Test Coverage section is updated in this PR.

The same table of cases is asserted in all three languages, so the parity is now pinned rather than incidental:

DELETE /containers/json	Deny
DELETE /containers/create	Deny
GET /containers/json	Allow (list endpoint)
DELETE /containers/mycontainer	Allow (real container)
GET /containers/mycontainer/json	Allow (reserved only in the name position)

Verified the tests fail without the fix — Go unit tests RED on all three reserved words, and the integration suite reports 404 instead of 403.

Verification

• make test-all, make lint-all — pass
• make test-integration{,-rs,-ts} — 30/30 each, identical output across all three

Scope note

Docker also has POST /containers/prune, which none of the three excludes. I checked it rather than assuming: it is consistently denied in all three (POST, no suffix match, falls to default-deny), so there is no parity gap and no behaviour change needed. Left alone deliberately.

[abienkowski]

Rebased onto 05320aa (post-#47 main) and re-verified on 2026-10-02: make test-all / make lint-all green, integration suites 30/30 in Go, Rust and TypeScript. Added b4dc457 updating AGENTS.md's test counts. Review follow-ups filed as #48 (Rust forwards DELETE /containers/ — empty name treated as a container) and #49 (TS path-wide exec deny; Go matchEndpoint subpath acceptance).