docs: Add 152 README files for ATA-21 air conditioning documentation structure

[Copilot]

Title

docs: Add 152 README files for ATA-21 air conditioning documentation structure

Summary

Addresses missing README files for 161 folders in ATA-21 documentation. Created 152 README files across 8 standard ATA-21 subsystems (21-00 through 21-70), each following identical 19-directory structure for AMM/IPC publications with CSDB subdirectories and SSOT master data.

Structure per subsystem:

├── PUB/AMM/ → CSDB/{APPLICABILITY,BREX,COMMON,DM,DML,ICN,PM} + EXPORT/
├── PUB/IPC/ → CSDB/{APPLICABILITY,BREX,COMMON,DM,DML,ICN,PM} + EXPORT/
└── SSOT/

README content: YAML front matter (classification, maintainer), context-aware descriptions parsed from path structure, standards compliance references (ATA iSpec 2200, S1000D, CSDB).

Subsystems covered: 21-00-air-conditioning-general, 21-10-compression, 21-20-distribution, 21-30-pressurization-control, 21-40-heating, 21-50-cooling, 21-60-temperature-control, 21-70-moisture-air-contamination-control.

Canon checks

• Bridge QS→FWD→UE→FE→CB→QB unchanged
• UTCS phrasing intact
• QOx = Quantum Optimizations
• PAx orientation markers: ONB/OUT only
• AMPEL360 remains commons (no app code)

CXP (Context eXchange Points)

• Update UTCS/context.manifest.json if applicable (N/A - documentation only)
• Update sbom/spdx.sbom.json if dependencies changed (N/A - no deps)
• cxp-publish passes in CI ✅

Evidence

• All CI checks pass
• Documentation updated (152 new README files)
• Tests added/updated (N/A - documentation structure)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>📚 README review checklist (ping @copilot)</issue_title>
<issue_description>📚 README review checklist (ping @copilot)

Folders touched in this PR: 161

❌ Missing README

• PRODUCTS/AMPEL360/AMPEL360_AIR_TRANSPORT/BWB-Q100/domains/EEE/ata/ATA-21/21-00-air-conditioning-general/PUB/AMM — add README.md (open folder)
• PRODUCTS/AMPEL360/AMPEL360_AIR_TRANSPORT/BWB-Q100/domains/EEE/ata/ATA-21/21-00-air-conditioning-general/PUB/AMM/CSDB/APPLICABILITY — add README.md (open folder)
• PRODUCTS/AMPEL360/AMPEL360_AIR_TRANSPORT/BWB-Q100/domains/EEE/ata/ATA-21/21-00-air-conditioning-general/PUB/AMM/CSDB/BREX — add README.md (open folder)
• PRODUCTS/AMPEL360/AMPEL360_AIR_TRANSPORT/BWB-Q100/domains/EEE/ata/ATA-21/21-00-air-conditioning-general/PUB/AMM/CSDB/COMMON — add README.md (open folder)
• PRODUCTS/AMPEL360/AMPEL360_AIR_TRANSPORT/BWB-Q100/domains/EEE/ata/ATA-21/21-00-air-conditioning-general/PUB/AMM/CSDB/DM — add README.md (open folder)
• PRODUCTS/AMPEL360/AMPEL360_AIR_TRANSPORT/BWB-Q100/domains/EEE/ata/ATA-21/21-00-air-conditioning-general/PUB/AMM/CSDB/DML — add README.md (open folder)
• PRODUCTS/AMPEL360/AMPEL360_AIR_TRANSPORT/BWB-Q100/domains/EEE/ata/ATA-21/21-00-air-conditioning-general/PUB/AMM/CSDB/ICN — add README.md (open folder)
• PRODUCTS/AMPEL360/AMPEL360_AIR_TRANSPORT/BWB-Q100/domains/EEE/ata/ATA-21/21-00-air-conditioning-general/PUB/AMM/CSDB/PM — add README.md (open folder)
• PRODUCTS/AMPEL360/AMPEL360_AIR_TRANSPORT/BWB-Q100/domains/EEE/ata/ATA-21/21-00-air-conditioning-general/PUB/AMM/EXPORT — add README.md (open folder)
• PRODUCTS/AMPEL360/AMPEL360_AIR_TRANSPORT/BWB-Q100/domains/EEE/ata/ATA-21/21-00-air-conditioning-general/PUB/IPC — add README.md (open folder)
• PRODUCTS/AMPEL360/AMPEL360_AIR_TRANSPORT/BWB-Q100/domains/EEE/ata/ATA-21/21-00-air-conditioning-general/PUB/IPC/CSDB/APPLICABILITY — add README.md (open folder)
• PRODUCTS/AMPEL360/AMPEL360_AIR_TRANSPORT/BWB-Q100/domains/EEE/ata/ATA-21/21-00-air-conditioning-general/PUB/IPC/CSDB/BREX — add README.md (open folder)
• PRODUCTS/AMPEL360/AMPEL360_AIR_TRANSPORT/BWB-Q100/domains/EEE/ata/ATA-21/21-00-air-conditioning-general/PUB/IPC/CSDB/COMMON — add README.md ([open folder](https://github.com/AmedeoPelliccia/ASI-T2/tree/335651c2aea8bff9e...

• Fixes **📚 README review checklist** (ping @copilot) #156

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