fix(claude-code): support retain tags env override

[koriyoshi2041]

Summary

• add the missing HINDSIGHT_RETAIN_TAGS override to the Claude Code config loader
• cover comma-separated tag parsing and precedence through load_config()
• document the override in the integration README and synced docs copies

Tests

• uv run pytest hindsight-integrations/claude-code/tests/test_config.py (22 passed)
• uv run ruff check hindsight-integrations/claude-code/scripts/lib/config.py hindsight-integrations/claude-code/tests/test_config.py
• uv run ruff format --check hindsight-integrations/claude-code/scripts/lib/config.py hindsight-integrations/claude-code/tests/test_config.py
• git diff --check

Closes #2896

[nicoloboschi]

Closing: superseded by Coding Agents, which now ships exactly this — your issue (#2896) is what prompted it.

retainTags joined the env surface in v0.2.0 on the existing convention (HINDSIGHT_ + the field in SCREAMING_SNAKE, still a fallback the config file wins over), as a comma-separated list:

HINDSIGHT_RETAIN_TAGS="project:{gitProject},env:work"

Entries are trimmed and blanks dropped, so a trailing comma is a typo rather than an empty tag reaching the API. The tags also take template placeholders, which was the other half of what people wanted them for. retainMetadata is deliberately file-only — map-valued settings don't survive flattening into one variable.

npx @vectorize-io/hindsight-coding-agents install claude-code (docs).