spec(v4): promote R4-P0-2 KLICKD_E_* user-facing error i18n table to normative (docs-only)

[Davincc77]

Summary

• Inscribes the normative user-facing error message contract (RFC 2119) for v4 user.klickd writers / readers in FR / EN / DE / LB as the docs-only companion to R4-P0-1 §3.4 (passphrase) and §3.6 (mandatory reload verification).
• Adds docs/spec/R4-P0-2-error-i18n-table.md covering every KLICKD_E_* code surfaced in the wizard, with: localized message FR/EN/DE/LB, recommended autonomous user action (no "contact support"), severity, recoverability, and a safe-disclosure rule (do not leak whether file vs passphrase failed where unsafe; do not name failing gate / missing field).
• Adds SPEC.md §33.12 cross-reference (mirrors §33.11 for R4-P0-1) and updates the docs/roadmap/ROAD-TO-V4-GA.md R4-P0-2 entry to reference the new normative artifact (status: contract inscribed).
• Introduces, docs-only, six new wizard-contract codes not yet in the v3.x SDKs: KLICKD_E_PASS_MISMATCH, KLICKD_E_SAVE_LOCAL, KLICKD_E_LEGACY_VERSION, KLICKD_E_CORRUPT, KLICKD_E_POLICY_LOCKED, KLICKD_E_UNSAFE_QR. SDK alignment is deferred to R4-P0-3 (Python) / R4-P0-4 (TypeScript).

Why this lands now

R4-P0-1 §3.4 and §3.6 already depend on a normative user-facing error contract; the bare v3.x identifiers (KLICKD_E_AUTH, _VERSION, _FORMAT, _KDF, _CIPHER, _WEAK_PASS, _SCHEMA) are unusable to non-developer end-users (anti-pattern A6). This PR closes that dependency without touching SDK / schema / vectors.

Scope (strict)

• ✅ Docs-only. No on-the-wire field, schema, or vector change.
• ✅ No SDK code modified (errors.py / errors.ts untouched).
• ✅ No package version bump, Git tag, GitHub release, npm / PyPI / Zenodo / DOI publication.
• ✅ No change to SPEC §33.7 forward-compatibility contract or §33.10 privacy invariants.
• ✅ No app i18n / UI implementation; wizard implementation remains hors-repo (klickd.app).

Coverage (R4-P0-1 wizard contexts)

Wizard context	Codes covered
Passphrase creation (R4-P0-1 §3.4)	KLICKD_E_WEAK_PASS, KLICKD_E_PASS_MISMATCH
Save / download (§3.5)	KLICKD_E_SAVE_LOCAL
Mandatory reload verification (§3.6)	KLICKD_E_AUTH, KLICKD_E_FORMAT, KLICKD_E_SCHEMA, KLICKD_E_VERSION, KLICKD_E_KDF, KLICKD_E_CIPHER
Import / decrypt (§3.1 secondary entry)	+ KLICKD_E_LEGACY_VERSION, KLICKD_E_CORRUPT
Legacy version / migration	KLICKD_E_LEGACY_VERSION
Corrupt / unsupported file	KLICKD_E_CORRUPT, KLICKD_E_FORMAT, KLICKD_E_KDF, KLICKD_E_CIPHER
Locked policy violation	KLICKD_E_POLICY_LOCKED
Unsafe QR / deeplink (V4-ONBOARDING-QR-DEEPLINK.md C1–C7)	KLICKD_E_UNSAFE_QR

Safe-disclosure rule (excerpt)

• KLICKD_E_AUTH message MUST remain ambiguous between wrong-passphrase and tampered-file.
• KLICKD_E_FORMAT / KLICKD_E_SCHEMA MUST NOT name specific missing envelope / payload fields to the user.
• KLICKD_E_POLICY_LOCKED MUST NOT name the specific failing gate.
• KLICKD_E_UNSAFE_QR MUST NOT echo the offending payload.
• Developer-mode diagnostics MAY include these details — must be opt-in and MUST NOT be auto-sent off-device (preserves §33.10 privacy invariants and R4-P0-1 §3.5 zero-network constraint).

Files changed

• docs/spec/R4-P0-2-error-i18n-table.md — new (~486 lines, normative)
• SPEC.md — +33 lines (§33.12 pointer)
• docs/roadmap/ROAD-TO-V4-GA.md — R4-P0-2 entry updated

Testing

• Markdown relative links resolve (verified script).
• 13 KLICKD_E_* rows, each with FR / EN / DE / LB columns + action + severity + recoverability + safe-disclosure.
• No new on-the-wire field, schema, or vector introduced (docs-only).
• SDK errors.py and errors.ts untouched.
• No package version, Git tag, or release artifact modified.
• CI: should be green (docs-only — no code paths touched).

Recommended next branch

R4-P0-3 — examples/v4/personas/ (5 downloadable persona profiles: élève terminale FR, chef de projet PME FR, dev full-stack EN, créateur média preview media.klickd, joueur RPG preview gaming.klickd). R4-P0-3 fixtures can land as preview artefacts referenced by R4-P0-1 §3.1 (the "I already have a user.klickd file → import" secondary path) ahead of strict P0-2 / P0-6 validation.

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