Add integration test harness, push/deploy + TUI tests, document two production bugs

[l-hellmann]

What Type of Change is this?

• New Feature
• Fix
• Improvement
• Release
• Other

Description (required)

Builds an in-process integration test harness for zcli commands and adds
unit-level UI tests for the bubbletea models. Includes minimal production-code
seams to enable testing without changing user-facing behavior. Also documents
two confirmed bugs as skipped regression tests (fixes intentionally left for
follow-up PRs to keep this one scoped to test infrastructure).

Production changes (small, backward-compatible)

• zeropsRestApiClient.NewAuthorizedClient accepts a full URL or a bare host;
  defaults the scheme to https:// when missing.
• cmdBuilder.RunRootCmd(rootCmd, RunOptions{Ctx, Args, Stdout, Stderr}) —
  new test-friendly entry point that returns an exit code instead of calling
  os.Exit. ExecuteRootCmd becomes a thin wrapper around it.
• logger.OutputConfig.Out accepts an io.Writer (defaults to os.Stderr),
  so uxBlock output can be captured.
• flagParams.New(notice io.Writer) routes "Using config file:" notices
  through the injected stderr.
• New env var ZEROPS_CLI_YAML_FILE_PATH overrides the per-user .zcli.yml
  location (parity with ZEROPS_CLI_DATA_FILE_PATH and ZEROPS_CLI_LOG_FILE_PATH).
• Empty ZEROPS_TOKEN env value no longer overrides a token persisted by
  zcli login — previously export ZEROPS_TOKEN= would silently log out.
• yamlReader.ResetCache() — exported so in-process test re-runs aren't
  served stale bytes from the package-level cache.

New tests

Integration (src/cmd/, //go:build devel, run via make test-integration):

• Harness with httptest.Server, per-test tempdir, login/scope seeding,
  archive decompression, and git fixture helpers.
• 14 service-push tests (happy paths, error paths, polling, scope, archive-file-path).
• 7 git-archive tests (not-init / zero-commits errors, workspace-state
  clean/staged/all, --deploy-git-folder).
• 1 service-deploy variant.
• 1 project-list, 1 login, 1 version.

TUI (src/uxBlock/models/, via github.com/charmbracelet/x/exp/teatest):

• selector (10): single + multi-select, filter-mode, esc, clamping, label.
• prompt (7): cursor movement, clamping, esc, initial position.
• input (5): typing, backspace, esc, empty submit, label render.
• table (11): renderer output, body indexing, deep clone, cell pretty-flag.

Confirmed bugs documented as skipped tests (pushDeploy_bugs_test.go)

1. --setup flag ignored when the service name happens to match a setup
   name in zerops.yaml (servicePush.go:85, serviceDeploy.go:72).
   Reproduced from a real pipeline running --setup showcase-backend on a
   service named "backend".
2. SIGSEGV nil-deref on apiProcess.AppVersion.Id / .Build
   (servicePush.go:235, :251) when a process poll returns
   status=RUNNING with appVersion: null. Crashes the binary from the
   spinner goroutine. Confirmed by removing the t.Skip in isolation; stack
   trace is in the test comment.

Both tests are committed as t.Skip'd reproductions so CI stays green;
removing the skip after each fix will lock the regression in.

Test plan

• make test — unit tests pass.
• make test-integration — 24 PASS + 2 SKIP, ~16 s.
• TUI tests pass — 33 across 4 packages, <1 s combined.
• Branch builds for darwin/arm64, linux/amd64, windows/amd64.
• make lint reports zero issues in src/ and cmd/ (after running
  tools/install.sh). The lint binary itself reports a pre-existing
  toolchain mismatch in golang.org/x/crypto/.../fips140only_go1.26.go
  when the developer has Go ≥1.26 installed; unrelated to this diff.

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