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

includes/core/class-prv-settings-renderer.php

@@ -38,6 +38,7 @@ class PRV_Settings_Renderer {
 		$this->render_styles();
 		echo '<div class="prv-settings-wrap">';
 		echo '<h1 class="prv-page-title">' . esc_html__( 'PR Vision — Settings', 'pr-vision' ) . '</h1>';
+		( new PRV_Costs_Renderer() )->render_subnav( 'settings' );
 		$this->render_notices();
 		echo '<div class="prv-card"><h2>' . esc_html__( 'Model Manager', 'pr-vision' ) . '</h2>';
 		( new PRV_Model_Manager_Table() )->render();
@@ -202,6 +203,11 @@ class PRV_Settings_Renderer {
 		$budget = PRV_Config::get_monthly_budget_usd();
 		echo '<div class="prv-field"><label class="prv-label" for="prv_monthly_budget_usd">' . esc_html__( 'Monthly budget cap (USD)', 'pr-vision' ) . '</label>';
 		echo '<input class="prv-input" style="max-width:160px;" type="number" min="0.01" step="0.01" id="prv_monthly_budget_usd" name="prv_monthly_budget_usd" value="' . esc_attr( number_format( $budget, 2, '.', '' ) ) . '" data-scoring-relevant="1"></div>';
+		// v0.3.0: I/O retention days.
+		$retention = PRV_Config::get_io_retention_days();
+		echo '<div class="prv-field"><label class="prv-label" for="prv_io_retention_days">' . esc_html__( 'Call I/O retention (days)', 'pr-vision' ) . '</label>';
+		echo '<input class="prv-input" style="max-width:120px;" type="number" min="1" step="1" id="prv_io_retention_days" name="prv_io_retention_days" value="' . esc_attr( (string) $retention ) . '">';
+		echo '<span class="prv-field-hint">' . esc_html__( 'Prompt + response text is auto-deleted after this many days. Cost and metadata are kept indefinitely.', 'pr-vision' ) . '</span></div>';
 	}
 
 	/**