fix: embed prompts as strings for Bun bundler compatibility

[usvimal]

Summary

• Embeds all prompt content as string constants instead of reading from .txt files at runtime
• Fixes compatibility issues with Bun's bundler where __dirname resolves incorrectly

Problem

When the package is bundled by Bun, the original approach using __dirname + readFileSync fails because __dirname resolves to incorrect paths at runtime. This causes errors like:

Cannot find module './lib/strategies' from 'C:\Users\...\node_modules\@tarquinen\opencode-dcp\dist\index.js'

ENOENT: no such file or directory, open '...\opencode-dcp\dist\lib\prompts\discard-tool-spec.txt'

Root Cause

Bun's bundler doesn't preserve __dirname semantics correctly when files are bundled. The .txt files exist in the package, but the runtime path resolution fails.

Solution

Embed all prompt content directly as string constants in lib/prompts/index.ts. This:

• Eliminates filesystem access at runtime
• Ensures compatibility with Bun and other ESM bundlers
• Maintains the same loadPrompt() API

Testing

Tested locally by patching the installed package in ~/.cache/opencode/node_modules/@tarquinen/opencode-dcp/ - the errors are resolved and the package works correctly.

Changes

• lib/prompts/index.ts: Replaced readFileSync approach with embedded string constants

[Tarquinen]

Is this necessary? I don't think the bundler is even used?

[DamianB-BitFlipper]

I have been running in to the Error: ENOENT: no such file or directory, open '/Users/damianb/.cache/opencode/node_modules/@tarquinen/opencode-dcp/dist/lib/prompts/system/system-prompt-both.txt' every time opencode updates. I have to quit and reopen for it to work.

Unless the prompts are really big, I see nothing wrong with just having them as big strings in the plugin itself.

Love the plugin nonetheless!

[Tarquinen]

I have been running in to the Error: ENOENT: no such file or directory, open '/Users/damianb/.cache/opencode/node_modules/@tarquinen/opencode-dcp/dist/lib/prompts/system/system-prompt-both.txt' every time opencode updates. I have to quit and reopen for it to work.

Unless the prompts are really big, I see nothing wrong with just having them as big strings in the plugin itself.

Love the plugin nonetheless!

Good point, fixing this in a slightly different way than this PR in #272