Add prompt templating system with mustache

- Add promptsDir to Paths.hs for $AVA_DATA_ROOT/prompts/
- Create Omni.Agent.Prompts module with:
  - Mustache template loading and rendering
  - Automatic partial resolution via automaticCompile
  - Frontmatter/metadata parsing for list command
- Create omni-agent-prompt CLI for previewing prompts:
  - list: show all available prompts
  - render: render prompt with --var and --json context
- Prompts use .mustache extension for automaticCompile compatibility
- Partials referenced with full extension: {{> shared/memory.mustache}}

1 files changed, 4 insertions, 0 deletions

diff --git a/Omni/Agent/Paths.hs b/Omni/Agent/Paths.hs
index 6df6991..d8def78 100644
--- a/Omni/Agent/Paths.hs
+++ b/Omni/Agent/Paths.hs
@@ -8,6 +8,7 @@
 module Omni.Agent.Paths
   ( avaDataRoot,
     skillsDir,
+    promptsDir,
     outreachDir,
     userScratchRoot,
     userScratchDir,
@@ -33,6 +34,9 @@ avaDataRoot =
 skillsDir :: FilePath
 skillsDir = avaDataRoot </> "skills"
 
+promptsDir :: FilePath
+promptsDir = avaDataRoot </> "prompts"
+
 outreachDir :: FilePath
 outreachDir = avaDataRoot </> "outreach"