feat(pair): huh forms for prompts (TTY-gated, legacy fallback)

[ironystock]

Summary

Final phase of the Charmbracelet polish sprint (Phase 4 of `~/.claude/plans/peppy-forging-dahl.md`). Three pair-flow prompts now render through `huh` in real terminals; the legacy bufio implementations are preserved verbatim and still fire when stdout isn't a TTY.

Prompt	TTY path	Non-TTY path
`promptForServerURL`	`huh.NewSelect` + `huh.NewInput` on "Other"	`promptForServerURLLegacy` (numbered menu)
`promptForDefaultNamespace`	`huh.NewSelect` with explicit skip option	`promptForDefaultNamespaceLegacy` (numeric index)
`confirmFileMerge` (F24)	`huh.NewConfirm` ("Yes, merge" / "No, skip")	`confirmFileMergeLegacy` (`[Y/n]` bufio)

Gating logic

Each new wrapper:

```go
if !isTTY(out) {
return *Legacy(in, out, ...)
}
// ...huh form...
```

`isTTY` (added in `render.go` for Phase 3) returns false for any writer that isn't a `*os.File` — including the `*bytes.Buffer` and `io.Discard` that `pair_flow_test.go` uses. Result: every existing pair test exercises the legacy path and passes unchanged.

Why keep the legacy functions

Three reasons, all carry-forward from CLAUDE.md:

1. Tests + scripted use need them. Gating preserves both UX modes. Removing the legacy path would mean either rewriting the test suite against a `pty` harness (overkill) or losing test coverage entirely (worse).
2. The `pair_flow_test.go::TestPair_F24_*` tests are load-bearing and pin behavior the F24 issue depended on (Brad's dogfooding scenario where `.mcp.json` got clobbered silently).
3. They're tiny (~25 lines each) and have stable behavior.

Verification

• `go build ./...` clean.
• `go test ./...` green. All 12 `TestPair_*` cases pass:
  • 4 F24 sub-tests (preflight, accept-on-yes, no-prompt-on-missing, default-yes-on-empty)
  • 4 server URL prompt sub-tests (default, choice 1, choice 2, pasted URL)
  • Namespace prompt + skip-on-empty
  • Hostname/sentinel client_name, server-returned name, persistence, write-per-config-target
• Manual: `./bin/rememberize.exe pair ` in a real terminal will now show huh's arrow-key picker for server URL + namespace + the F24 confirm — same flow, prettier UI.
• Manual non-TTY: `echo "" | ./bin/rememberize.exe pair ` falls through to the legacy bufio path (provable with `script`/`tee`/etc.).

Sprint complete

This closes the original 5-phase plan:

• ✅ Phase 0 — refactor split (#7)
• ✅ Phase 1 — leveled logger + flags (#10 part 1)
• ✅ Phase 2 — fang wrap (#10 part 2)
• ✅ Phase 3 — lipgloss tables (#18)
• ✅ Phase 4 — this PR
• ⏭ Phase 5 — tag `v0.1.0` (yours per AGENTS.md early-weeks rule)

Plus side-quests landed along the way: CI hardening (#11), branch protection ruleset, Blacksmith migration (#16), 4 dependabot bumps (#12-15), API key preflight (#19), styled install.sh (#20).

Test plan

• CI green across the 6 required checks.
• Manual smoke after merge in a real terminal: `rememberize pair ` shows the huh-styled flow.
• If anything looks off in huh (cell padding, color contrast in your terminal theme), tweak in a follow-up before tagging.

🤖 Generated with Claude Code

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