feat(style): gateway outcome glyphs for blocked/allowed/warned (#84)

[mattcollie]

Summary

Adds gateway-derived outcome glyphs to Arai's human-readable output surfaces,
replacing generic warning/blocked icons with a coherent visual vocabulary that
mirrors the gateway metaphor. Closes #84 (parent #64). Follow-on to #83.

Glyph set

Outcome	Unicode	ASCII fallback
Blocked	●·│✕	o.|x
Allowed	│●│	|o|
Warned (Warn + Inform)	●·│	o.|

Visual weight tracks severity: blocked is heaviest (dot outside + ochre cross),
warned is medium (dot adjacent, pre-passage), allowed is lightest (dot passing
through, centered).

Unicode detection (should_use_unicode)

Precedence: ARAI_ASCII (non-empty) → ASCII; NO_UNICODE (non-empty) → ASCII;
else locale priority LC_ALL > LC_CTYPE > LANG (first non-empty, UTF-8 check);
missing/empty locale → ASCII. Deliberately TTY-independent — piped output
honours the same locale as interactive output.

Palette reuse from #83

The ochre cross (✕) reuses #83's passage() helper and the should_colorize()
gate. Colour appears only on the blocked glyph's cross, and only when
colorize=true. Every other glyph character carries no colour.

Carve-outs

• Hook output (src/hooks.rs): all outcome_glyph calls pass literal false
  for colorize — glyph characters appear in Pre/Post human strings but zero ANSI
  escape bytes are emitted, even under CLICOLOR_FORCE=1.
• --json output: no outcome_glyph call on any JSON code path — glyph-free by
  design (structural, not conditional).
• Audit-chain ✓/✗ integrity markers (src/main.rs) are left untouched
  (different semantic — hash-chain verification, not outcome display).

Integration surfaces

• src/main.rs: cmd_audit and cmd_why human-output rows prefixed with the glyph.
• src/stats.rs: print_compliance_section replaces the generic ⚠ with the warned glyph.
• src/hooks.rs: Pre/Post human strings prefixed with glyphs; colorize hard-coded false.

Zero new dependencies

src/style.rs extended in-place. Cargo.toml / Cargo.lock unchanged.

Test coverage

584 tests pass (0 failures). New: tests/gateway_outcome_glyphs.rs (9 integration),
tests/gateway_glyphs_verifier.rs (29 independent verifier tests), plus style unit
tests. Full gate: cargo fmt --check clean, cargo clippy 0 new warnings, cargo test 584/584.

Provenance

Built via the Taniwha dispatch cycle (design v6 → contract → leaf → verifier).
The glyph direction (bar+dot, closest to the line+ochre-dot brand mark) was a
user decision at the design gate. Full audit trail under .taniwha/kupu/.

🤖 Generated with Claude Code

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