Post-audit reliability hardening — wave 2 (medium + deferred)

[LeadcodeDev]

Wave 2 of the post-audit chantier — the medium findings, plus three items wave 1
deliberately deferred. Parent: #102 · Sub-issues: #109 #110 #111

One commit per workstream.

Theme

Wave 1 fixed the things that produced wrong output. Wave 2 fixes the things that
produced no output and no complaint — properties the schema accepts and the engine
silently ignores. Every item here is the same defect wearing a different hat.

	Before	After
white-space	read in 2 places repo-wide, neither of them the painter — so unwrappable_text_overflow fired on a state the renderer could not produce	honoured in measurement and painting, on text, gradient_text and caption
rich_text	no intrinsic → measured 0×0 → rendered nothing without an explicit width	measures itself; a long single span now wraps internally instead of only at span boundaries
glow	stored, never read; renders with and without were byte-identical	renders, in the configured colour
Misplaced color / font_size	warning; render exited 0 with default styling	both fail
{"durration": 3.0} on a scene	silently ignored	rejected, names the field
Missing duration	data did not match any variant of untagged enum SceneEntry	scenes[1]: missing field \duration``
11px text on a 1080p frame	validates clean	advisory warning
color: "ligth-blue"	rendered magenta at render time (wave 1)	fails validation
schema::GridTrack and 7 more dead types	exported, shadowing the live CSS types	removed

Verification

cargo test --workspace → 580 passed, 0 failed. cargo clippy --workspace --all-targets
clean. All 7 examples/*.json still validate under the stricter rules — none needed
weakening to pass.

Independent acceptance harness (fixtures written from the audit findings, not borrowed
from the implementing agents; pixel-measured where the claim is visual): 13/13 green,
including wave-1 non-regression checks.

Notes for review

• The legibility threshold is evidence-based, not a guess. 1.2% of output height
  (~13px on 1080p), chosen by rendering a line at 8–28px and downscaling 50% — the way
  video is actually watched. Everything below 14px became a grey smear. Expressed as a
  fraction so it holds on 4K and vertical canvases, and it clears every shipped
  component default so it does not fire on already-clean scenarios.
• --strict-attrs is now inert (unknown attributes error by default, so it has
  nothing left to promote). Rather than leave a flag that silently does nothing — the
  same defect this PR is about — it is kept for script compatibility and prints a
  deprecation notice.
• nowrap text gets min-width: 0. Without it, CSS automatic minimum size lets a
  nowrap text grow its own box past its flex container and silently resize siblings.
  With it, the box stays clamped and the line bleeds past it, which is what a browser
  does.

Known follow-ups, deliberately not in this PR

• Animating glow_radius / glow_intensity as raw keyframe properties still produces a
  black halo: GlowConfig.color is not plumbed into that path, which lives in
  css/animation.rs.
• cmd_validate's blocking check never accounts for unresolved_vars, so a scenario
  with only unresolved $variable refs reports valid while render refuses it.
• Badge's size→font-size table is duplicated in geometry.rs because
  BadgeSize::params() is private to the components crate. It will drift silently.
• Colour validation covers CssStyle's Color-typed fields only. Component-specific
  plain-String colour fields (Table.header_color, Marquee.color, chart series, …)
  still go through the lenient path.