docs: add shared operational memory under .claude/memory

[ecv]

Summary

Adds a version-controlled .claude/memory/ directory holding the public,
repo-portable subset of operational knowledge for working on this repo with
Claude Code (or any agent). One file per fact, indexed by MEMORY.md.

Opened as a draft for review of both the selection and whether this belongs
in-tree.

What's included

File	Why it's here
gh-issue-body-file.md	Use --body-file not a --body heredoc so code fences render
github-sub-issues-via-graphql.md	Sub-issues have no native gh command; use the addSubIssue GraphQL mutation
pull-main-on-switch.md	Always git fetch + pull --ff-only on switching to main
unattended-loop-permission-discipline.md	How to run a hands-off /loop with zero permission prompts
activity-policies-owned-by-source-repos.md	This repo owns its own ActivityPolicy CRs under config/services/activity/policies/, shipped via an OCI bundle — plus the recurring unguarded-responseObject DLQ-leak pattern

What's deliberately excluded

Operational notes that are environment-specific or sensitive were left out:
prod alert-triage and incident catalogues, access-control internals, Flux/gateway
production incidents, e2e project IDs and gitignored values files, and
deploy-repo Flux paths. Nothing here contains credentials, cluster names,
project IDs, or internal-only incident detail.

Notes

• Sourced by gleaning a separate project's local agent memory and keeping only
  the items that are both useful here and safe to publish.
• The activity-policies-* entry overlaps the area touched by feat(iam): re-home audit-log-querier inheritance to activity service #677.

🤖 Generated with Claude Code

[ecv]

Considering this in a public repo. RFC.