[FEATURE] Prompt history recall — Ctrl+R search + inline autosuggestions (zsh-autosuggestions style)

Problem

Reusing past prompts in Claude Code is painful. There's no way to:

• Search through prompts you've typed before
• Get inline suggestions as you type (like zsh-autosuggestions)

Current workaround: copy-pasting from external notes (I've been using WeChat's file transfer assistant as a scratchpad 😅).

Project-specific prompts are too narrow to justify a full /skill file, but broad enough that I type them repeatedly across sessions.

Proposed Solution

Two complementary features, in order of implementation complexity:

1. Ctrl+R — Fuzzy search over prompt history (lower effort)

• Every submitted prompt is saved to a history store (similar to shell ~/.zsh_history)
• Ctrl+R opens a fuzzy search picker (fzf-style) over past prompts
• Selected prompt fills the input box (not auto-submitted — user can edit first)
• History scoped by project directory, with option to search all-projects

2. Inline autosuggestions while typing (higher effort, higher value)

• As the user types, a gray ghost-text suggestion appears showing the best-matching past prompt
• → or Tab accepts the suggestion (does not submit — fills input for further editing)
• Identical UX to zsh-autosuggestions / Warp Terminal's command history
• Fallback gracefully if no match found (no ghost text shown)

Why this matters

The input box already supports up-arrow history cycling (see #32400, #15631), but that's sequential, not searchable. For users who reuse project-specific prompts frequently, fuzzy search is an order-of-magnitude better UX.

Related issues: #25877 (predictive text), #32400 (history scoping), #26304 (agent Ctrl+R)