chore(configure): surface reader.ReadString errors in remaining wizard prompts

[cristim]

Context

golangci-lint (with errcheck.check-blank: true) flags every _, _ := reader.ReadString('\n') / _, _ := f() site in the configure wizards. Most of these sites pre-date PR #1279, which only patched the four sites it introduced (commit a526f1a). The Lint Code job stays failing on main because of the remaining sites — they need a sweep.

Memory entries that this touches:

• feedback_no_silent_fallbacks.md — return an explicit error rather than discarding it.

Pre-existing sites (file:line:column at PR #1279 HEAD a526f1a)

cmd/configure_azure.go

• 380:18 — azureStepListSubscriptions: subscriptionID, _ := reader.ReadString('\n')
• 493:10 — promptAndRunExplicitCommand: choice, _ := reader.ReadString('\n')
• 529:13 — executeExplicitCommand: response, _ := reader.ReadString('\n')

cmd/configure_gcp.go

• 186:14 — getGCPCredentialsFilePath: credsFile, _ = reader.ReadString('\n')
• 563:13 — gcpStepSelectProject: projectID, _ := reader.ReadString('\n')
• 701:10 — promptAndRunGCPCommand: choice, _ := reader.ReadString('\n')
• 736:13 — executeGCPCommand: response, _ := reader.ReadString('\n')

(All seven existed on main before PR #1279; same shape, only the line numbers shifted with that PR.)

Acceptance

• All seven reader.ReadString sites surface the error per the same pattern PR refactor(configure): replace az/gcloud CLI shell-outs with native SDK calls #1279 already used for its four sites: choice, err := reader.ReadString('\n'); if err != nil { return ..., fmt.Errorf("failed to read ...: %w", err) }.
• golangci-lint run ./cmd/... passes (or at least the errcheck lines for these files drop to zero).
• Existing wizard tests still pass; no behaviour change beyond "interactive flow fails loud on closed stdin instead of running the default action".

Out of scope

• The broader errcheck sweep across internal/api/*, internal/auth/*, internal/mocks/* etc. that the same lint run reports — those are independent of the configure wizards and should be tracked in a separate sweep issue if not already.

[cristim]

Verification sweep against main (101f099fb) on 2026-07-27 finds this already resolved.
Every reader.ReadString call site now checks its error.
Evidence: commit 86a385a, plus the SDK-migration series.
Recommending close.

[cristim]

Verified resolved at 3c0f8ac: all reader.ReadString sites in the configure wizards bind and check err; configure_azure.go funnels every prompt through readTrimmedLine, which returns the error (tolerating io.EOF only when a final unterminated line carried data), and the three configure_gcp.go prompts each wrap the error with fmt.Errorf. Evidence: cmd/configure_gcp.go:661,695,731 and cmd/configure_azure.go:44 (86a385a). Residual axes checked: grepped cmd/ for the blank-discard forms , _ := reader and , _ = reader and for every ReadString call including cmd/helpers.go:221 - all check err; the only remaining _ = sites in configure_gcp.go are deferred f.Close and os.Remove on the key-write rollback path, which are not read errors. Closing as completed; reopen if the behaviour recurs.