docs: add team usage guide

[carlosmoradev]

🔗 Linked Issue

Closes #305

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🏷️ PR Type

• type:docs — Documentation only

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📝 Summary

• Adds docs/TEAM-USAGE.md with the scope mental model (project vs personal), the lingua franca convention for shared memory, and a clear description of what scope does and does not do today.
• Documents the current sync contract honestly: scope filters search and context reads but does not filter sync. Both scopes leave the machine when the project is enrolled.
• Links the new guide from DOCS.md, the README nav, and the mem_save scope parameter description so it is discoverable from the obvious entry points.

📂 Changes

File	Change
docs/TEAM-USAGE.md	New guide: scope mental model, language strategy, what to save where, current sync behavior, related docs.
DOCS.md	Add Team Usage row in the docs table; link the guide from the mem_save scope param description.
README.md	Add Team Usage to the top nav.

🧪 Test Plan

• Unit tests pass locally: go test ./... (no code changes; ran as a sanity check)
• E2E tests pass locally: go test -tags e2e ./internal/server/... (no code changes; ran as a sanity check)
• Read the new guide top to bottom to verify all links resolve and all claims match current code

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✅ Contributor Checklist

• Linked an approved issue (Closes #305)
• Added exactly one type:* label (type:docs)
• Ran unit tests locally
• Ran e2e tests locally
• Docs updated (this PR is the doc update)
• Commit follows conventional commits format
• No Co-Authored-By trailers

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💬 Notes for Reviewers

• While drafting this I checked the sync path and found that internal/sync/sync.go exports every observation of an enrolled project regardless of scope. The issue's framing suggested scope: personal stayed local, which is not what the code does today. The guide describes the current behavior and lists two workarounds (separate project name, or do not enroll the shared project).
• If scope-aware sync filtering is desired in the future, it deserves its own design decision and code change. Happy to open a follow-up issue if you want to track it.
• Per the engram-docs-alignment skill rule, the guide describes current behavior, not intended behavior. Every claim in docs/TEAM-USAGE.md is verifiable against the current code.

[carlosmoradev]

Heads up: I do not have permission to add labels on this repo, so type:docs is missing. Whenever a maintainer can add it, the "Check PR Has type:* Label" gate will pass.

[Alan-TheGentleman]

I added the type:docs label and #305 is approved. One content change before this merges: align the sync-boundary wording with the feedback left on the earlier #331 so the guide does not overstate what cloud sync shares across machines. Update that section and push, then I will merge.

[Alan-TheGentleman]

Thanks @carlosmoradev — solid work, and the guide is accurate and complete. I pushed two commits to your branch as a maintainer edit:

1. Resolved the merge conflict with main — the scope line in DOCS.md now keeps the newly added global value and your Team Usage link.
2. Tightened the sync-boundary wording to match the docs: add team usage guide #331 review — the guide now states explicitly that sync operates "by project/session association, not by scope", so personal-scope observations in an enrolled project still replicate.

Once CI is green this is ready to merge. Thanks for sticking with it.

[Alan-TheGentleman]

Merge conflict with main resolved and the sync-boundary wording aligned with the #331 review (sync by project/session association, not scope). Content verified. Approving.