feat: peptide-geo-monitor v0.1.0 — AI-visibility dashboard

Add initial plugin implementation per the CTO engineering handoff
(geomonitor/threads/2026-06-ai-visibility-v1/01-cto-eng-handoff.md).

## What
- PGM_Probe_Provider interface + PGM_Probe_Result value object
- PGM_Perplexity_Provider (sonar via OpenRouter/CF AI Gateway)
- PGM_OpenRouter_Provider (GPT-search + Gemini-search, generic parameterised)
- PGM_Gateway_Client: shared HTTP + exponential-backoff retry (mirrors PRAB)
- PGM_Citation_Detector: domain extraction, is_cited(), get_our_position()
- PGM_Cost_Ledger: MTD cost from DB, can_afford() pre-check, hard monthly cap
- PGM_Probe_Runner: peptides×intents×models run, budget abort, in-run cache
- PGM_Table_Manager: pgm_ai_visibility dbDelta, schema-version, drop_table()
- PGM_Config: typed getters, seed_defaults() (12 peptides, 3 intents, 3 models)
- PGM_Cron: weekly pgm_weekly_probe schedule/clear
- PGM_Data_Collector + PGM_Dashboard_Panel interfaces (seam for future panels)
- PGM_Collector_Registry: singleton registry
- PGM_Ai_Visibility_Collector: trendline, standings, MTD cost (score formula)
- PGM_Ai_Visibility_Panel: proxy note, Chart.js trendline, standings table
- PGM_Admin_Page: GEO Monitor menu, Run now POST handler (nonce+capability)
- uninstall.php: DROP TABLE + DELETE pgm_* options + wp_clear_scheduled_hook
- Unit tests (6 files): citation detection, score calc, cost ledger + budget
  abort, provider response parsing (mock HTTP), cron, uninstall purge
- ARCHITECTURE.md, CONVENTIONS.md, CONTEXT.md (score formula), README.md,
  CHANGELOG.md — same-commit per DoD
- CI workflow: PHP lint (8.1/8.2/8.3) + PHPCS + 300-line check

## Security
- Secrets from wp-config constants only; none hardcoded
- manage_options + nonce on every admin action
- Input sanitized; output escaped

Agent-Session: geomonitor v0.1.0

CHANGELOG.md

@@ -0,0 +1,35 @@
+# Changelog — Peptide GEO Monitor
+
+All notable changes to this project will be documented in this file.
+
+Format: [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
+Versioning: [Semantic Versioning](https://semver.org/)
+
+---
+
+## [0.1.0] — 2026-06-13
+
+**Initial release — AI-visibility dashboard.**
+
+### Added
+
+- `PGM_Probe_Provider` interface + `PGM_Probe_Result` value object.
+- `PGM_Perplexity_Provider`: Perplexity `sonar` via OpenRouter/Cloudflare AI Gateway; parses `citations[]` array.
+- `PGM_OpenRouter_Provider`: generic parameterised provider for GPT-search and Gemini-search models; parses annotations + inline URL regex fallback.
+- `PGM_Gateway_Client`: shared CF AI Gateway HTTP client with exponential-backoff retry and cURL auth injection (mirrors PRAutoBlogger pattern).
+- `PGM_Citation_Detector`: domain extraction from citation arrays/URLs, `is_cited()`, `get_our_position()`.
+- `PGM_Cost_Ledger`: month-to-date spend from DB, `can_afford()` pre-check, `update_row_cost()` settlement.
+- `PGM_Probe_Runner`: full peptides × intents × models run with budget cap abort, in-run cache, and partial-run persistence.
+- `PGM_Table_Manager`: `{prefix}pgm_ai_visibility` via `dbDelta`, schema-version option, `drop_table()` for uninstall.
+- `PGM_Config`: typed getters + `seed_defaults()` with ~12 peptides, 3 intents, 3 models.
+- `PGM_Cron`: weekly `pgm_weekly_probe` WP-Cron; `schedule_weekly()` / `clear_schedule()`.
+- `PGM_Data_Collector` + `PGM_Dashboard_Panel` interfaces (collector/panel seam).
+- `PGM_Collector_Registry`: singleton registry for future extensibility.
+- `PGM_Ai_Visibility_Collector`: trendline (per-run visibility score), standings (per-peptide latest), MTD cost.
+- `PGM_Ai_Visibility_Panel`: proxy-metric note, Chart.js trendline, per-peptide standings table, MTD cost bar, "Run now" button.
+- `PGM_Admin_Page`: "GEO Monitor" top-level menu, Chart.js enqueue, Run now POST handler (nonce + `manage_options`).
+- `uninstall.php`: DROP TABLE + DELETE `pgm_*` options + `wp_clear_scheduled_hook`.
+- Unit tests: citation detection, score formula, cost ledger + budget cap abort, provider response parsing (mock HTTP), cron registration, uninstall purge.
+- `ARCHITECTURE.md`, `CONVENTIONS.md`, `CONTEXT.md` (incl. visibility score formula), `README.md`.
+- CI: PHP lint (8.1/8.2/8.3) + PHPCS + 300-line check (mirrors `peptide-repo-core`).
+- Seed config: 12 peptides, 3 prompt intents, Perplexity sonar + GPT-4o-search + Gemini-2.0-Flash.