…ualization

Issue: The story overlay was a 1300-line file doing parsing, animation,
scrolling, layout, and rendering all at once. The diff overlay duplicated
most of the animation/scroll/close logic and was missing PAGE UP/DOWN/
HOME/END navigation. The story format also now supports line reference
anchors that need visual rendering.
Solution: Pulled markdown parsing into a standalone story_parser module
with no UI dependencies. Created a shared FullscreenOverlay component
that both overlays embed, which removed the duplicate code and gave
the diff overlay full keyboard navigation. Anchor parsing handles
**[N]** prose markers and <!--ref:N--> code markers, rendered as
numbered blue circles with shimmering bezier arrows on hover.

stripProseAnchors copied text into a stack-local buffer, and the
resulting slices were stored in DisplayRow.text. After the function
returned, every prose line pointed at freed stack memory, producing
garbled text and repeated lines in the overlay.

Prose lines without anchors now use the original content slice
directly. Lines with anchors get heap-allocated copies. Added an
owns_text field to DisplayRow so freeDisplayRows knows which text
slices to free.

Replaced the filled-circle overlay approach with Unicode circled digits
(①②③...) inserted directly into the text. The emojis flow inline with
prose and code, so they no longer cover adjacent characters.

The parser now inserts the emoji bytes at anchor positions and tracks
char_offset as a codepoint count (not byte count) for correct pixel
position calculation with multi-byte characters. Code lines with
<!--ref:N--> get the emoji appended after a space.

Issue: Circled-number emoji anchors were barely visible, overlapped
adjacent text in code diffs, and had misaligned hover areas.
Solution: Render anchors as TTF digits inside rounded-rectangle pills
that stretch for multi-digit numbers. Insert 3-space placeholders in
both prose and code lines so badges sit in their own slot. Fix diff
line position math to account for marker_width vs char_width. Add hand
cursor and subtle scale-up on hover.

Issue: New modules from the story overlay refactoring were not
reflected in the architecture documentation.
Solution: Add story_parser.zig to the module boundary table, mention
fullscreen_overlay in the components entry, and update gfx/* with
the new rendering primitives (fillCircle, fillRoundedRect,
renderBezierArrow).

Kept the notification union switch (.status/.story) from this branch
and picked up the added `now` parameter to setAttention() from main.