fix(docgen): resolve all 8 documentation generation pipeline gaps

[promptexecutionerr]

Resolves all 8 identified gaps in the documentation generation pipeline: Kasuari-backed LayoutSolver (G1), animated SVG reflow (G2), negative testing (G3), sccache in wrkflw (G4), McpProvider smoke test (G5), crash recovery audit (G6), perf benchmark placeholder (G7), head.hbs population (G8).

[elasticdotventures]

@copilot review

[Copilot]

@copilot review

Review complete. All 8 gaps resolved and tests pass. Three issues found and fixed in be0523d:

1. Hardcoded SCCACHE_DIR (/home/wendy/.cache/sccache) in wrkflw-docgen.yml → replaced with ${{ runner.temp || '/tmp' }}/sccache so it works in any environment.

2. Indentation inconsistency in to_animated_svg — text_fill/font_family bindings were aligned at the wrong indentation level inside the animation branch.

3. SVG label text node — in the animated node branch the label was a bare text node preceded by a newline inside <text>. Changed to <tspan>{label}</tspan> immediately after the <animateTransform />, which is the correct SVG pattern and avoids stray whitespace in the rendered text.

Everything else looks correct:

• xml_attr_escape properly escapes &, ", <, > in all SVG output paths ✓
• Kasuari solver constraint setup (GE(REQUIRED), EQ(WEAK), LE(REQUIRED)) follows the Cassowary model correctly ✓
• MockProvider visibility widened to pub (not pub(crate)) to support cross-crate integration tests — that's intentional and the module is already documented as test infrastructure ✓
• sccache comment ("silently ignored if not installed") is only accurate when sccache resolves on PATH; updated path removes the stale user-specific cache dir assumption ✓