Fast Path Pipeline: Path selection UI + wizard routing

Part of #557

## Problem

Users need a way to choose between the fast path and the agent path. When a Dockerfile is detected, we should present the fast path as the recommended default, with clear time estimates so users can make an informed choice.

## Changes

- **`PathSelectionStep.tsx`** — the decision point UI showing three options:
- "Deploy now" (recommended, ~3-5 min) — deterministic templates, no AI wait
- "Deploy now + AI suggestions" (~3-5 min + async PR) — fast deploy plus Copilot improvement PR later
- "Full AI generation" (~15-40 min) — existing agent path
- **`WizardShell.tsx` modifications** — add routing logic: after repo readiness check, if Dockerfiles found, show PathSelectionStep. User's choice routes to either fast path or agent path orchestration.
- Wire up the fast path orchestration hook to the wizard when the user picks a fast path option

Start with PathSelectionStep.tsx and WizardShell.tsx, then trace the wizard's repo readiness check and fast path orchestration hook. Implement the three documented choices, show the fast path when Dockerfiles are detected, and route each choice to the specified orchestration path with the stated time estimates.

Written by the indexing model from the issue text.