docs(phase1-step2): §11 RESOLVED — apply Q1-Q6 with three tightenings (v2)

Reviewer pass on docs/PHASE1-STEP2-DESIGN.md by Mickael + Claude chat
2026-04-30. All 6 questions in §11 closed. Three of the six carried
tightenings, all baked into the body of the doc.

Q1: APPROVED. Exact list only for v1 PLUGIN_TOOL_FILTER.

Q2: APPROVED with tightening — lock `tool_name` in immutable-identity-
    fields list alongside transport / agent / correlation_id /
    client_id / operation_id. §6 mutation contract now has an
    explicit table of immutable fields. A plugin must veto if it
    wants different routing — silent rewrite would break audit
    pairing. Two new §9.4 tests cover the filter behaviour.

Q3: APPROVED. Defer pre_llm_call / post_llm_call to a later step.

Q4: APPROVED with tightening — specify the audit envelope for
    plugin-raised exceptions. New `hook_error` event in §7.5 with
    required fields plugin_name, hook_name, error_type, error
    (truncated to _PREVIEW_MAX = 200 chars), inheriting
    correlation_id of the wrapping operation. `level: "warning"`,
    not "error" — operation still succeeded, only the plugin
    failed; keeps audit_report's error-rate metric meaningful.
    `hook_fired` and `hook_error` are split events, never both
    for the same call. §1.1 audit-event column updated for every
    hook lifecycle. §9.5 added 5 new tests (envelope shape,
    correlation_id inheritance, level=warning, truncation,
    no-double-emit).

Q5: APPROVED. No cap in hook layer.

Q6: APPROVED with rename — on_session_start / on_session_end →
    on_operation_start / on_operation_end. HookCtx field
    session_id → operation_id. Reasoning: matches Step 1 §1.4
    correlation_id contract vocabulary ("operation"); avoids
    collision with the existing voice_session_start /
    voice_session_end Step-1 audit events (those keep their
    names — narrower scope, literal voice sessions). Mass-rename
    touched 21 lines across §1.1, §1.4, §2.2, §2.3, §2.5, §5,
    §6, §7.2, §7.3, §9.2, §9.5, §12, §13.

Doc header updated v1 → v2; closing line updated.
Section count unchanged (§0–§13). 954 lines total. SOH bytes: 0
(verified post-commit). No code modified. _HTTP_BLOCKED untouched.
PM2 untouched.

Ready for the implementation prompt.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: Mikarina13