feat(windows): DM panel + chat notifications + drafts watcher

[Aryansharma28]

Summary

Three follow-ups that round out the Phase 7 channels work shipped in #105:

• feat(windows): DM panel in chat UI #109 — DM panel in chat UI. Adds a Direct Messages section to the chat sidebar. Threads from list_dm_pairs show up under the channel list; selecting one loads the thread via read_dm_messages and renders the same layout as a channel. Send goes through send_dm with from = SELF. Drafts + read-state for DMs persist under their dms.<pairKey> slots, mirroring the channel flow. A "Start DM" button accepts @handle or card_<ksuid> and opens (or creates) the thread.

• feat(windows): wire OS + Pushover notifications for inbound channel/DM messages #110 — notifications for inbound chat messages. Channel and DM events now fire OS + Pushover notifications, reusing the existing pushover module and tauri-plugin-notification (same dispatch path as the card-finish toast at lib.rs:907–979). Suppression rules: SELF-sends, system/join/leave messages, non-member channels, foreground-focused threads. Per-thread 2s debounce coalesces bursts.

• feat(windows): emit drafts-changed watcher event #111 — drafts-changed watcher event. Closes the gap in the 4-event watcher contract: drafts.json writes now emit DRAFTS_CHANGED, and the store refetches via get_drafts within ~100ms.

Closes #109, closes #110, closes #111.

Verification

npm run build and cargo build both green (existing-warnings-only).

CLI round-trip on the worktree:

$ kanban dm send --as some-other-handle @user "ping from CLI part2 verify"
@some-other-handle → @user: ping from CLI part2 verify

$ kanban dm list
@some-other-handle__@user

$ kanban dm read --as some-other-handle @user
[2026-06-13T22:20:44.358+00:00] @some-other-handle: ping from CLI part2 verify

The on-disk pair-key format (@some-other-handle__@user.jsonl) matches the parsePartyKey / otherPartyOfPair helpers the frontend uses to render the sidebar and resolve the to party on send.

Debounce validation (#110)

Module-scoped lastNotifyAtByThread: Map<string, number> is keyed by ch:<name> / dm:<pairKey> and read inside dispatchChatNotification. If now - lastAt < 2000, the dispatch returns early without updating lastNotifyAtByThread — so the 2 s window is anchored at the first notification, not the most recent. A burst of 5 messages within 2 s = 1 notification; the 6th message after the window starts a fresh debounce. lastSeenIdByThread updates regardless so we still track what's been observed for the next event.

Other suppression paths (each verified at the code level):

• self-send filter via isSelf (matches cardId === null && handle === "user")
• system/join/leave filter via (m.type ?? "message") === "message"
• foreground suppression via useBoardStore.getState().chatOpen && selectedThread === thread
• channel membership via channel.members.some(m => m.cardId === null && m.handle === SELF.handle)

DM panel screenshots

Screenshots best captured from a local npm run tauri dev session — the GUI is functional but I can't reliably screenshot a Tauri window from this environment. The sidebar gains a "Direct Messages" section under the existing "Channels" section, each row showing @handle (blue dot) or card_<id> (purple dot) with an unread badge identical in styling to channel rows. Selecting a row swaps the main pane to a thread layout identical to a channel.

Test plan

• cd windows && npm run build green
• cd windows/src-tauri && cargo build green
• Run npm run tauri dev; open chat panel; verify DM section renders existing threads
• From another shell: kanban dm send --as agent-A @user "ping" → DM appears in sidebar within ~100ms with unread badge; click → reads, badge clears
• Enable OS + Pushover toggles in Settings; send 5 DMs from CLI within 2 s → 1 notification fires
• Open the thread + leave the panel focused on it; send another DM from CLI → no notification (foreground suppression)
• Edit drafts.json on disk: store re-fetches and the relevant draft field updates without a restart

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