fix(gateway): isolate soul by chat

[ymote]

Summary

• Store gateway /soul overrides under a profile/channel/chat-scoped session path instead of the shared profile data root.
• Read/write/reset /soul using the inbound message profiled base session key so Telegram/Discord chats and profiles do not overwrite each other.
• Append the scoped soul override when spawning new session actors so the setting takes effect for new sessions.
• Add regressions for chat isolation, profile isolation, topic base-key sharing, and reset not clearing soul for another chat.

Closes #626

Current refresh

• Base: origin/main 1df02bd
• Head: 72b3ff9
• Refreshed from a clean isolated clone; no generated artifacts or untracked files included.

Validation

• git diff --check origin/main...HEAD
• rustfmt --check crates/octos-cli/src/gateway_dispatcher.rs crates/octos-cli/src/session_actor.rs crates/octos-cli/src/soul_service.rs
• cargo fmt --all -- --check
• CARGO_TARGET_DIR=/private/tmp/octos-1222-refresh-target CARGO_INCREMENTAL=0 CARGO_PROFILE_DEV_DEBUG=0 cargo test -p octos-cli soul_service::tests -- --nocapture (7 passed)
• CARGO_TARGET_DIR=/private/tmp/octos-1222-refresh-target CARGO_INCREMENTAL=0 CARGO_PROFILE_DEV_DEBUG=0 cargo test -p octos-cli gateway_dispatcher::tests::should_isolate_soul -- --nocapture (2 passed)
• CARGO_TARGET_DIR=/private/tmp/octos-1222-refresh-target CARGO_INCREMENTAL=0 CARGO_PROFILE_DEV_DEBUG=0 cargo test -p octos-cli gateway_dispatcher::tests -- --nocapture (34 passed)
• CARGO_TARGET_DIR=/private/tmp/octos-1222-refresh-target CARGO_INCREMENTAL=0 CARGO_PROFILE_DEV_DEBUG=0 cargo clippy -p octos-cli --all-targets --no-deps
• CARGO_TARGET_DIR=/private/tmp/octos-1222-refresh-target CARGO_INCREMENTAL=0 CARGO_PROFILE_DEV_DEBUG=0 cargo clippy -p octos-cli --all-targets --features api --no-deps (exits 0 with existing unrelated warning noise)
• git status --short --branch and git ls-files --others --exclude-standard in the isolated clone show no untracked/generated files.

Notes

• Full clippy with -D warnings remains blocked by pre-existing warnings outside this slice, so this refresh records the clean exit of the repository-standard clippy invocation without widening the PR.

CI / merge status

• GitHub CI is green on head 72b3ff9a7b728617a34058b09545ecc2436b13af: check, test-octos-cli, test-octos-agent (lib), test-octos-agent (integration), dashboard, swarm-app, check-matrix, typos, and author-email passed. Optional platform/e2e/security expansion jobs were skipped by workflow conditions.
• Current GitHub state remains MERGEABLE but branch-protection blocked by required review (BLOCKED / REVIEW_REQUIRED).
• Bug: Soul Configuration Not Properly Isolated Across Multiple Profiles/Users #626 should close through this PR after review and merge; no manual closure was performed.

[ymote]

Current-main validation for #626 on 2026-05-29.

Validated PR head 3733aed1a8da98ad693d88c9dc3d0690049de6c3 by cleanly merging it onto current origin/main 1fb4c88e020242d82cee245b331798ed6dc551e7 in /private/tmp/octos-1222-current-Cl0yOk; local rehearsal merge commit was 62beb8a313907e89f8709f5c956a334ed4d96c57.

Acceptance evidence:

• /soul read/write/reset now use a profiled base chat key, so profile/channel/chat isolate the soul while topic sessions for the same chat share it.
• SessionActor appends the scoped soul for the spawned session key when building the system prompt.
• Tests cover per-chat isolation, per-profile isolation, topic sharing for the same chat, and reset not clearing another chat soul.

Commands run:

• git diff --check origin/main...HEAD passed.
• rustfmt --check crates/octos-cli/src/gateway_dispatcher.rs crates/octos-cli/src/session_actor.rs crates/octos-cli/src/soul_service.rs passed.
• cargo test -p octos-cli soul_service::tests -- --nocapture passed: 7 passed.
• cargo test -p octos-cli gateway_dispatcher::tests::should_isolate_soul -- --nocapture passed: 2 passed.
• cargo test -p octos-cli gateway_dispatcher::tests -- --nocapture passed: 34 passed.
• cargo clippy -p octos-cli --all-targets --no-deps passed.
• cargo clippy -p octos-cli --all-targets --features api --no-deps passed with existing warnings.

Environment: rustc 1.95.0 (59807616e 2026-04-14), cargo 1.95.0 (f2d3ce0bd 2026-03-21), Darwin 25.5.0 arm64. Build/test artifacts were confined to /private/tmp/octos-1222-current-1fb4-*; git ls-files --others --exclude-standard was empty after validation.

Remaining gap: cargo fmt --all -- --check still fails on current-main formatting drift outside this PR diff, observed in crates/octos-cli/src/api/ui_protocol_ledger.rs. GitHub reports this PR as MERGEABLE but branch protection is BLOCKED because review is still required, so I did not merge it.