PR Vision v0.3.0: per-call cost accountability + LLM call audit trail

P0 security:
- PRV_Gateway_Client: remove response body from RuntimeException (HTTP status only)
- PRV_Capture_Writer: allowlist-only write (prompt/response text, never headers/auth)
- Mandatory capture order: can_afford → probe → persist_result → update_row_cost → write_meta → capture_io
- capture_io last and wrapped in swallowing try/catch

New tables (SCHEMA_VERSION 3):
- prv_call_meta: cost/metadata per call, kept indefinitely
- prv_call_io: rendered prompt + raw response, pruned on retention window (default 90d)

New classes:
- PRV_Call_Meta_Table, PRV_Call_Io_Table: table schema + dbDelta
- PRV_Capture_Writer: metadata + I/O write; security allowlist enforced
- PRV_Prune_Cron: daily prv_daily_prune cron deletes aged prv_call_io rows only
- PRV_Cost_Rollup_Query: MTD summary, model breakdown, drill-down, projection
- PRV_Call_Log_Query: paginated + filtered call-log query + per-call I/O fetch
- PRV_Costs_Page + PRV_Costs_Renderer: Costs admin sub-page (cap progress, bento, model table, drill-down)
- PRV_Call_Log_Page + PRV_Call_Log_Table_Renderer: Call Log admin sub-page (filter bar, paginated table, WCAG AA pagination)
- PRV_Call_Drawer_Renderer: non-modal complementary drawer (5 states: Normal/Pruned/Legacy/Failed/Loading)
- PRV_Call_Drawer_Script: inline JS for drawer (300-line split from renderer)
- PRV_Call_Detail_Ajax: wp_ajax_prv_call_detail AJAX handler
- PRV_Admin_Page_Css: CSS provider (300-line split from PRV_Admin_Page)
- PRV_Probe_Run_Executor: inner probe loop (300-line split from PRV_Probe_Runner)

Updated:
- PRV_Probe_Result: tokens_in/tokens_out params + getters
- Both providers: report tokens_in/tokens_out from usage.prompt_tokens/completion_tokens
- PRV_Probe_Runner: slimmed to lock+UUID+delegation; injects PRV_Capture_Writer
- PRV_Config: get_io_retention_days(); PRV_IO_RETENTION_DEFAULT_DAYS constant
- PRV_Upgrader/Activator/Deactivator/Plugin: register new tables, cron, pages, AJAX
- Settings: retention days field + save in controller
- uninstall.php: DROP both new tables, clear prv_daily_prune cron
- Subnav 4-tab strip (Dashboard | Costs | Call Log | Settings) on all pages
- ARCHITECTURE.md, CHANGELOG.md, CONTEXT.md, CONVENTIONS.md updated

Tests:
- test-capture-writer.php: write_meta, write_io, P0 security (401 record has no key/Bearer/sk-or-)
- test-cost-audit.php: MTD reconciliation, projection, prune, forced capture_io exception, table drops

Agent-Session: peptiderepo-geomonitor-v0.3.0-cost-audit

CONVENTIONS.md

@@ -1,6 +1,6 @@
 # Conventions — PR Vision
 
-**Version:** 0.2.1 | **Last updated:** 2026-06-14
+**Version:** 0.3.0 | **Last updated:** 2026-06-15
 
 Applies to all contributors and AI agents working in this repo. Where this document and `AGENT-OPERATING-STANDARD.md` conflict on process, the Standard wins; this document wins on code style.
 
@@ -92,3 +92,12 @@ All key reads must go through `PRV_Key_Store::get_key()`. This maintains the pre
 - AJAX handlers: call `PRV_Key_Store::get_key()` before any LLM call.
 - New provider that needs the key: implement `is_configured()` as `'' !== PRV_Key_Store::get_key()`.
 - Do NOT pass the resolved key to any client-side surface, log, exception message, or `error_log()`.
+
+## 9. Capture pattern (v0.3.0+)
+
+The call-audit trail follows a strict allowlist pattern:
+
+- `PRV_Capture_Writer::write_meta()` accepts only: `visibility_row`, `run_id`, `peptide_slug`, `model`, `intent_label`, `tokens_in`, `tokens_out`, `cost_usd`, `latency_ms`, `cited`, `http_status`, `config_version`.
+- `PRV_Capture_Writer::write_io()` accepts only: the rendered `prompt_text` (plain text) and `response_text` (LLM response content).
+- **NEVER** pass `$headers`, `$parsed_args`, `Authorization`, raw HTTP request blobs, or any field not in the above lists.
+- Capture calls are LAST in the probe loop and wrapped in a swallowing try/catch — failure must never propagate to the probe path or corrupt cap accounting.