Add language-specific prompt injection for toolchain guidance

- Add language_prompts module that auto-detects programming languages in workspace
- Scan for language files with depth limit (2) to inject relevant toolchain prompts
- Add prompts/langs/ directory for language-specific markdown files
- Include Racket/raco toolchain guidance as first language prompt
- Update combine_project_content() to accept language_content parameter
- Integrate language detection into main CLI flow and agent mode
- Update project memory with new feature documentation

prompts/langs/racket.md

@@ -0,0 +1,30 @@
+RACKET LANGUAGE CODE EXPLORATION + RACO TOOLING
+
+- Core `raco` commands to rely on:
+  - Documentation & discovery:
+    - `raco docs <id>` to open docs for identifiers, modules, or packages.
+  - Compilation & checks:
+    - `raco make <file.rkt>` to force compilation and surface errors early.
+  - Testing:
+    - `raco test <path>` to run `module+ test` blocks and test files.
+  - Packages & dependencies:
+    - `raco pkg show` to inspect installed packages and their locations.
+    - `raco pkg show <pkg>` to inspect package metadata and versions.
+  - Profiling & performance:
+    - `raco profile <file.rkt>` for CPU hot spots.
+  - Debugging & stack traces:
+    - `racket -l errortrace <file.rkt>` (or enabling errortrace) for readable stack traces.
+
+- Structural analysis tools (use when reasoning about non-trivial codebases):
+  - `raco dependency-graph <path>`:
+    - Use to visualize or reason about module dependencies and layering.
+    - Identify cycles, high fan-in “core” modules, and accidental coupling.
+  - `raco modgraph`:
+    - Use for quick textual inspection of module graphs when visualization isn’t needed.
+  - Treat dependency graphs as architectural signals, not just diagrams.
+
+- `racket -e`-driven exploration:
+  - Use the one-shot script execution to:
+    - `require` modules incrementally and inspect exports.
+    - Probe functions with small concrete examples.
+    - Validate assumptions about data shapes and return values.