fix(spec): resolve 5 autonomous-actionable C30 findings in errors.md

[dp-web4]

C30 Remediation — core-spec/errors.md

REMEDIATION turn (by alternation) for the C30 audit (PR #268, MERGED). Applies the 5 AUTONOMOUS-actionable findings plus the opportunistic I1 banner, all inside web4-standard/core-spec/errors.md. 1 file changed, +18/−10. No design decisions taken; no other files touched.

Findings applied

ID	Sev	Fix
A-M1	MED	Align worked-example titles to the §2 normative taxonomy (§1 "Binding Failed"→"Binding Already Exists"; §3.1 "Unauthorized"→"Authorization Denied") and make §3.1 a coherent denied (not scope) case via its detail
A-M2	MED	type → OPTIONAL (default about:blank, RFC 9457 §3.1, matches SDK); code labelled a Web4 extension member (§3.2); Web4 deliberately mandates status/title
A-M3	MED	status is HTTP-modelled but transport-agnostic (CBOR/QUIC, BLE GATT, CAN per core-protocol §5.1)
A-L1	LOW	instance path segments are illustrative; no normative path registry
B-M1 §1	MED	Rescope: errors.md = the core protocol error taxonomy; SAL/ACP/metering/MCP subsystems extend it (autonomous half only)
I1	INFO	Add Version/Status/Last-Updated banner

Key discipline note (BC#5 corpus sweep)

The mandated pre-finalization sweep found the conformance vector test-vectors/errors/error-taxonomy.json (authz_denied_with_detail, labelled "spec §3.1 example") and test_errors.py pin the §3.1 example to W4_ERR_AUTHZ_DENIED/401/"Authorization Denied". The audit's A-M1 option (a) (switch to AUTHZ_SCOPE/403) would have broken that vector + required a coordinated SDK edit (out of bounds). Took the audit's equally-sanctioned option (b) instead — fix title + make the detail a genuine capability-denial, preserving code/status. Net effect: improves spec↔vector consistency. All four examples now match their §2 taxonomy titles.

Deferred (per audit routing)

• DESIGN-Q (operator): B-H1 numeric-vs-string error-system canonicity; B-M1 centralize-vs-distribute ownership; B-M3 W4IDp form.
• CROSS-TRACK (other files): B-M2 web4:// SSOT mirroring in data-formats; metering parallel-name reconcile; I2 QUICK_REFERENCE type-URI. NEW: web4-handshake.md:218 carries the same "Unauthorized" title mismatch (recorded for handshake re-audit).

🤖 Generated with Claude Code

[dp-web4]

APPROVED: C30 remediation of core-spec/errors.md, 1 file (+18/−10), no drift. Aligns the worked-example titles to the §2 normative taxonomy (Binding Already Exists, Authorization Denied), correctly relaxes type to OPTIONAL with code as an RFC 9457 §3.2 extension member while Web4 still mandates status/title, adds the transport-agnostic status note and the subsystem-extends scoping. Credit for the BC#5 corpus sweep: choosing option (b) to preserve test-vectors/errors/error-taxonomy.json + test_errors.py rather than breaking the conformance pin — improves spec↔vector consistency. DESIGN-Q and cross-track items correctly deferred. Development-phase aligned.