feat(parity): full Linux feature set — hb-view font rendering, SQLite hardening, lookup aliases

Linux reaches 100% of the render surface: render_font_text gains a
HarfBuzz engine (hb-view → real glyph outlines with full shaping, RTL
included) selected by capability — CoreText stays primary on darwin,
hb-view covers Macs without a Swift toolchain, and the <text>
placeholder remains the terminal fallback. hb-view exits 0 with empty
glyph defs on an unreadable font, so visible-text-without-paths counts
as a failed render. Symbols run offline-mode by default off-darwin
(live Swift paths are impossible there) with the librsvg hint, and the
sips leg is skipped where it cannot exist.

SQLite hardening from the container findings: busy_timeout now precedes
journal_mode (a WAL switch is a write), boot pragmas + migrations retry
on SQLITE_BUSY for up to 30s (concurrent first boot on one volume), and
every VACUUM runs with file-backed temp storage so a 10 GB database
cannot OOM a small VM. read_doc accepts documentation/-prefixed and
doc:// spellings via normalizeIdentifier. knip ignoreDependencies
pruned to the real unresolvables.