docs: collapse native-storage mode enum to local|cloud

[andrei-hasna]

Summary

• Collapse the obsolete local / remote / hybrid three-mode storage enum in docs/native-storage.md to the binary local | cloud model (cloud = AWS RDS + optional S3).
• Note that @hasna/cloud shared runtime is retired; cloud storage is explicit opt-in via HASNA_TODOS_STORAGE_MODE=cloud.
• Reframe Hybrid/Remote CRUD sections as Cloud Deployment sync and Cloud CRUD; preserve adapter API names and non-enum uses of "remote" (e.g. adapter.remote.*, remote_artifact_store).

Closes docs cleanup for task c4195198 (epic 56ed8b94).

Test plan

• grep -rniE '\bhybrid\b' docs/native-storage.md returns nothing
• grep -n 'HASNA_TODOS_STORAGE_MODE=' docs/native-storage.md shows only local and cloud values
• grep -nE '=remote|=hybrid' docs/native-storage.md returns nothing

Notes

Intentional docs/code drift remains: src/storage/config.ts still parses remote|hybrid until a future code-migration task. Design task 5ede7a57 may refine wording further.

[andrei-hasna]

Automated merge review: not merge-ready, so I did not merge this PR.

Hard blockers:

• Docs/runtime mismatch: this PR changes docs/native-storage.md to document HASNA_TODOS_STORAGE_MODE=cloud, but the runtime still defines/parses local | remote | hybrid in src/storage/config.ts; cloud currently throws HASNA_TODOS_STORAGE_MODE must be local, remote, or hybrid.
• The PR diff changes only docs/native-storage.md, so no source/tests update the mode contract. Focused storage tests still assert remote and hybrid.
• CI is not green: test failed in run 28750766138 / job 85249294182 with EACCES failures in src/lib/event-hooks.test.ts via src/lib/sync-utils.ts; dashboard passed.
• Branch freshness is unresolved: compare main...head is diverged, ahead_by=1, behind_by=4; base main is a508d390985030bc81c0a0f7b81e30d5e7f55242, head is 302b332054c767c1a0b29e721402d7725d562f28.
• No GitHub reviews or review requests are recorded; this lifecycle requires non-author review.

Local validation run in the isolated worktree:

• bun run typecheck passed.
• bun run test:no-cloud passed: 17 tests.
• bun test src/storage/storage.test.ts -t "parses explicit native remote RDS and S3 config|supports plain todos storage fallbacks|builds a hybrid local plus Postgres sync adapter" passed: 3 tests.
• Direct parser check: local, remote, and hybrid parse; cloud rejects.

Created follow-up todos task 94874d9d to resolve the mode-contract blocker before this PR is reconsidered for merge.

[andrei-hasna]

Worker update for task 94874d9d-4590-45b2-aace-4121d8e3bc13:

• Pushed fast-forward update to this PR head: 9faf81f.
• Resolved the native storage docs/runtime mismatch by keeping the implemented local|remote|hybrid contract and removing HASNA_TODOS_STORAGE_MODE=cloud docs.
• Fixed the event-hooks CI portability issue by removing hard-coded /home/hasna/.cache HOME fixtures.
• Local validation passed: focused storage/CLI/event-hooks/plan-artifacts tests, typecheck, test:no-cloud, full bun test, build, verify:release, staged redaction scan.
• GitHub CI is green on run 28756604433: test job 85264669499 succeeded; dashboard job 85264669504 succeeded. PR mergeStateStatus is CLEAN.

Remaining blocker: non-author review. Attempting to request selected reviewer kriptoburak failed via GitHub REST with HTTP 422: Reviews may only be requested from collaborators; kriptoburak is not currently a collaborator of hasna/todos. Follow-up todo created: e93a91dd-441a-4e8a-be95-e7068fb33a88. Manual action required: add/select a valid non-author collaborator reviewer, then approve or merge PR #42.