Local prompts not working in CLI despite documented support

### Checks

- [x] I have searched [github.com/aws/amazon-q-developer-cli/issues](https://github.com/aws/amazon-q-developer-cli/issues?q=) and there are no duplicates of my issue
- [x] I have run `q doctor` in the affected terminal session
- [x] I have run `q restart` and replicated the issue again

### Operating system

macOS 14.6.1 (23G93)

### Expected behaviour

Based on the [Amazon Q IDE documentation](https://docs.aws.amazon.com/amazonq/latest/qdeveloper-ug/context-prompt-library.html):
Local prompts should be stored in ~/.aws/amazonq/prompts/ (or similar location)
Prompts should be accessible via @prompt-name syntax
/prompts command should list local prompts alongside MCP prompts

Q generated bug report attached

[bug-report-local-prompts.md](https://github.com/user-attachments/files/21106884/bug-report-local-prompts.md)

### Actual behaviour

/prompts list only shows MCP prompts, ignoring local files
@prompt-name returns "Prompt not found" for all local prompts
No error messages or debug information about local prompt loading

### Steps to reproduce

Create prompt file: ~/.aws/amazonq/prompts/test-prompt.md
Add content: "You are a helpful assistant."
Run: q chat
Try: @test-prompt
Result: "Prompt test-prompt not found"

### Environment

```yaml

[q-details]
version = "1.12.3"
hash = "65aa9285fc7ec3716215386a89d3a626500a25a7"
date = "2025-07-03T01:14:12.212107Z (5d ago)"
variant = "full"

[system-info]
os = "macOS 14.6.1 (23G93)"
chip = "Apple M1"
total-cores = 8
memory = "8.00 GB"

[environment]
cwd = "/Users/USER/Projects/mcp-servers"
cli-path = "/Users/USER/Projects/mcp-servers"
os = "Mac"
shell-path = "/Applications/Amazon Q.app/Contents/MacOS/qchat"
install-method = "brew"

[env-vars]
PATH = "/opt/homebrew/bin:/opt/homebrew/sbin:/usr/local/bin:/System/Cryptexes/App/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin:/Users/USER/.local/bin:/Users/USER/.local/bin:/Users/USER/.local/bin"
Q_SET_PARENT_CHECK = "1"
SHELL = "/bin/zsh"
TERM = "xterm-256color"
__CFBundleIdentifier = "dev.warp.Warp-Stable"
```