[bfs2021]

Problem

Fixes #288. The TUI form pre-fills examples/sample_wordlist.txt and rejects an empty Wordlist field, but that path only exists inside a checkout: subenum -tui from go install, a release archive or the Docker image fails on the first ctrl+r with cannot read wordlist: open examples/sample_wordlist.txt. The command line has no such requirement — a missing -w scans with the bundled top-5000 list — so the TUI could not reach the default list the CLI uses.

Root cause

formFields[fieldWordlist] carried def: "examples/sample_wordlist.txt" and validate returned "Wordlist path is required" for an empty value, while loadWordlistCmd only ever called wordlist.LoadWordlist(path, domain), which opens a file. Nothing in the TUI could produce the bundled list, so an installed binary had no way to scan without a wordlist file of its own.

Fix

• The Wordlist field is optional: validate keeps the stdin rejection (- would read the stdin Bubble Tea owns) and drops the empty rejection.
• loadWordlist (new, in model.go) reads the file named on the form, or, when the field is empty, walks data.Subdomains5k through wordlist.NewPreparer/EachLine — the same path prepareWordlist uses for a missing -w, so normalization, dedupe and the per-domain length clamp match the CLI.
• beginScan adds the CLI's notice (using the bundled top-5000 list), so the scan view says which list ran.
• The field loses the repo-relative default and its required marker; the placeholder is empty = bundled top-5000 list. README's TUI section and the CHANGELOG say the wordlist is optional.

Testing

• New TestEmptyWordlistUsesBundledList starts a scan from an empty Wordlist field in simulation mode and asserts the loaded entries come from the bundled list and the scan view names it. Before the fix it fails with the issue's own symptom: form error: Wordlist path is required.
• TestNewFormModelDefaults and TestFormViewRows pin the empty default and the new row/placeholder.
• go test ./... — all packages pass (root 10.9s, internal/tui, internal/scan, pkg/subenum included).
• gofmt -l internal/tui — clean.
• golangci-lint run — could not run locally: this machine's golangci-lint was built against an older Go (export-data version 5 vs 2), so it refuses to typecheck go1.27 packages. Lint is left to CI.
• Not covered: an interactive render of the form inside an installed binary; the field value and the scan notice are asserted in the tests above.

[bfs2021]

Rebased onto current main (d0c56f0) to clear the conflict with the new TUI fields from #274/#262; the empty-wordlist behaviour and its row pin are unchanged, go test ./... is green again.