docs: add code-scroll mode design spec

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/superpowers/specs/2026-03-16-code-scroll-design.md

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+# Code Scroll Mode — Design Spec
+
+**Date:** 2026-03-16
+**Branch:** feat/code-scroll
+**Status:** Approved
+
+---
+
+## Overview
+
+Add a `--code` CLI flag that puts MAINLINE into "source consciousness" mode. Instead of RSS headlines or poetry stanzas, the program's own source code scrolls upward as large OTF half-block characters with the standard white-hot → deep green gradient. Each scroll item is one non-blank, non-comment line from `engine/*.py`, attributed to its enclosing function/class scope and dotted module path.
+
+---
+
+## Goals
+
+- Mirror the existing `--poetry` mode pattern as closely as possible
+- Zero new runtime dependencies (stdlib `ast` and `pathlib` only)
+- No changes to `scroll.py` or the render pipeline
+- The item tuple shape `(text, src, ts)` is unchanged
+
+---
+
+## New Files
+
+### `engine/fetch_code.py`
+
+Single public function `fetch_code()` that returns `(items, line_count, 0)`.
+
+**Algorithm:**
+
+1. Glob `engine/*.py` in sorted order
+2. For each file:
+   a. Read source text
+   b. `ast.parse(source)` → build a `{line_number: scope_label}` map by walking all `FunctionDef`, `AsyncFunctionDef`, and `ClassDef` nodes. Each node covers its full line range. Inner scopes override outer ones.
+   c. Iterate source lines (1-indexed). Skip if:
+      - The stripped line is empty
+      - The stripped line starts with `#`
+   d. For each kept line emit:
+      - `text` = `line.rstrip()` (preserve indentation for readability in the big render)
+      - `src` = scope label from the AST map, e.g. `stream()` for functions, `MicMonitor` for classes, `<module>` for top-level lines
+      - `ts` = dotted module path derived from filename, e.g. `engine/scroll.py` → `engine.scroll`
+3. Return `(items, len(items), 0)`
+
+**Scope label rules:**
+- `FunctionDef` / `AsyncFunctionDef` → `name()`
+- `ClassDef` → `name` (no parens)
+- No enclosing node → `<module>`
+
+**Dependencies:** `ast`, `pathlib` — stdlib only.
+
+---
+
+## Modified Files
+
+### `engine/config.py`
+
+Extend `MODE` detection to recognise `--code`:
+
+```python
+MODE = (
+    "poetry" if "--poetry" in sys.argv or "-p" in sys.argv
+    else "code" if "--code" in sys.argv
+    else "news"
+)
+```
+
+### `engine/app.py`
+
+**Subtitle line** — extend the subtitle dict:
+
+```python
+_subtitle = {
+    "poetry": "literary consciousness stream",
+    "code":   "source consciousness stream",
+}.get(config.MODE, "digital consciousness stream")
+```
+
+**Boot sequence** — add `elif config.MODE == "code":` branch after the poetry branch:
+
+```python
+elif config.MODE == "code":
+    from engine.fetch_code import fetch_code
+    slow_print("  > INITIALIZING SOURCE ARRAY...\n")
+    time.sleep(0.2)
+    print()
+    items, line_count, _ = fetch_code()
+    print()
+    print(f"  {G_DIM}>{RST} {G_MID}{line_count} LINES ACQUIRED{RST}")
+```
+
+No cache save/load — local source files are read instantly and change only on disk writes.
+
+---
+
+## Data Flow
+
+```
+engine/*.py (sorted)
+    │
+    ▼
+fetch_code()
+    │  ast.parse → scope map
+    │  filter blank + comment lines
+    │  emit (line, scope(), engine.module)
+    ▼
+items: List[Tuple[str, str, str]]
+    │
+    ▼
+stream(items, ntfy, mic)   ← unchanged
+    │
+    ▼
+next_headline() shuffles + recycles automatically
+```
+
+---
+
+## Error Handling
+
+- If a file fails to `ast.parse` (malformed source), fall back to `<module>` scope for all lines in that file — do not crash.
+- If `engine/` contains no `.py` files (shouldn't happen in practice), `fetch_code()` returns an empty list; `app.py`'s existing `if not items:` guard handles this.
+
+---
+
+## Testing
+
+New file: `tests/test_fetch_code.py`
+
+| Test | Assertion |
+|------|-----------|
+| `test_items_are_tuples` | Every item from `fetch_code()` is a 3-tuple of strings |
+| `test_blank_and_comment_lines_excluded` | No item text is empty; no item text (stripped) starts with `#` |
+| `test_module_path_format` | Every `ts` field matches pattern `engine\.\w+` |
+
+No mocking — tests read the real engine source files, keeping them honest against actual content.
+
+---
+
+## CLI
+
+```bash
+python3 mainline.py --code        # source consciousness mode
+uv run mainline.py --code
+```
+
+Compatible with all existing flags (`--no-font-picker`, `--font-file`, `--firehose`, etc.).
+
+---
+
+## Out of Scope
+
+- Syntax highlighting / token-aware coloring (can be added later)
+- `--code-dir` flag for pointing at arbitrary directories (YAGNI)
+- Caching code items to disk