docs: Add Gold Standard metered energy cooking v1.2 and v2.0 policies

[gautamp8]

This adds the Metered & Measured Energy Cooking Devices (MECD) methodology to the Methodology Library, in two versions:

• v1.2 — the version used for the first fully digital MECD issuance (ATEC × Earthood, GS11815 / GS11817, Bangladesh, 2024). Refreshed .policy bundle (MECD-v1.2-13-APR-2026) and modernised readme.
• v2.0 — the Paris-Agreement-aligned (PAA) revision that GS published in 2025. New .policy bundle, full readme with screenshots, migration guide, sanitised cURL test scripts, and realistic ER fixtures derived from the verified ATEC project.

Folder layout

Methodology Library/Gold Standard/Metered Energy Cooking/
├── MECD v1.2/
│   ├── MECD-v1.2.policy
│   └── readme.md
└── MECD v2.0/
    ├── MECD-v2.0.policy
    ├── readme.md
    ├── migration-from-v1.2.md
    ├── screenshots/             # 5 UI captures of the canonical M1/Electric flow (ER = 1193.4 tCO2e)
    ├── test-curls/              # 1 PDD + 7 ER curls covering all method × project-fuel combinations
    └── test-fixtures/           # 3 realistic JSON fixtures + parameter map + Node helper

What's in v2.0

• MECD-v2.0.policy — the policy bundle, ready to import into Guardian.

• readme.md — cookstove context, methodology summary, role-by-role workflow (Project Proponent / VVB / Standard Registry), important schemas, conservativeness stack explained for non-technical readers, embedded screenshots from a real run.

• migration-from-v1.2.md — practical upgrade guide: who needs to migrate when, new PDD/MR fields required by v2.0, expected credit-volume impact (15–35% reduction per period plus one-time embodied leakage), and what changes for each role.

• test-curls/ — sanitised cURL scripts (auth tokens stripped, IDs replaced with placeholders). All 7 ER curls validated against the ER document schema's full required-field tree (zero gaps) and pp_er_calcs (positive ER). Per-stove ER lands around 0.8 tCO2e/stove/yr — matches the 0.8154 value Earthood verified for ATEC under v1.2.

  Curl	Method	Project fuel	ER (tCO2e/yr)
  02-er-method-1-electricity.txt	M1 (WBT)	Electricity	1193
  02-er-method-1-fossil.txt	M1 (WBT)	LPG	1256
  02-er-method-1-renewable.txt	M1 (WBT)	Biogas	1608
  02-er-method-2-electricity.txt	M2 (CCT)	Electricity	1213
  02-er-method-2-fossil.txt	M2 (CCT)	LPG	1253
  02-er-method-2-renewable.txt	M2 (CCT)	Biogas	1452
  02-er-method-3-fossil.txt	M3 (KPT)	LPG	1515

• test-fixtures/ — three realistic ER JSON fixtures (M1 / M2 / M3 × Electricity) sourced cell-by-cell from ATEC GS11817's verified Earthood calculation tool. Includes parameter-map.md (cell-by-cell provenance), run-fixture.js (Node helper for running a fixture against pp_er_calcs without a Guardian instance), and a fixtures-specific readme.

What changed for v1.2

• Replaced the MECD 431_V1.2.policy bundle with the latest MECD-v1.2.policy build (13-APR-2026).
• Rewrote the readme:
  • Dropped the dated "hackathon" framing and the obsolete "Project Inception Document + IOT Measuring Device + auto-credit-issuance" workflow that the current bundle no longer ships.
  • Replaced with the actual current workflow (PDD → Validation Report → MR → Verification Report → Mint), matching the schemas/blocks in the new policy.
  • Added the ATEC × Earthood live deployment as the headline case study.
  • Added a Quantification Methods section noting M1 + M2 (no M3 in v1.2).
  • Added a forward link to v2.0 with a short framing of what's different.
  • Replaced 16 dated 2023-era GitHub-user-images

Test plan

• Both .policy bundles import cleanly into Guardian
• All 7 v2.0 ER curls validate against the schema's required tree (0 missing fields per curl)
• All 7 v2.0 ER curls produce positive ER end-to-end through pp_er_calcs
• Per-stove ER on the M2 / Electricity curl matches Earthood's verified ATEC v1.2 value (0.81 tCO2e/stove/yr, vs. 0.8154 verified)
• Realistic JSON fixtures reproduce the same numbers when run via test-fixtures/run-fixture.js
• test-curls/readme.md documents the one calc quirk operators should know about (no_of_days_per_year: 0 workaround for the M2/Electricity baseline path)
• v1.2-specific UI screenshots (currently placeholder; v2.0 shots ship as the canonical visual reference since the workflow is identical)