feat: rich composer session @-mentions + inspect_peer (#1228)

* feat(web): feature-flagged rich composer for inline session @ mentions

Custom segmented contenteditable (not TipTap) inserts caret-local session
atoms from the existing @ picker and serializes to markdown links on send.
Textarea path remains default until flag parity dogfood.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(web): rich composer mention boundary + #1215 refs

Treat U+FFFC mirror atoms as word boundaries so @ after a session
token still opens autocomplete. Point comments at Fixes #1215.

Co-authored-by: Cursor <cursoragent@cursor.com>

* test(web): peer-stack e2e for rich composer session @ mentions (#1215)

Smoke: flag on, @ picker inserts inline session atom chip (not prose dump).
Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(web): preserve newlines in rich composer Enter-newline mode

Chromium splits contenteditable on Enter into block divs; serialize those
as \\n and insert <br> when parent leaves Enter unhandled (Shift+Enter /
enter-inserts-newline).

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(web): show @ badge when rich composer mentions flag is on

Dogfood was invisible: flag-off looks like a normal textarea, and flag-on
had no chrome. Surface a small @ badge when enabled.

* fix(web): rich session composer on by default (not a user setting)

The plan dual-path was an engineering kill-switch, not an opt-in. Default
to the segmented composer; only richMentions=0 disables. Drop the flag
badge and record a peer-stack motion proof covering chips + baseline UX.

* fix(web): make rich composer Shift+Enter create a visible newline

Trailing <br>+empty text node was a silent no-op at EOL. Use
insertLineBreak (ZWSP pad fallback), assert real \\n in peer e2e.

* feat(web): hover tooltips on rich composer session chips

Show full title, status, short id, and path on chip hover via a portal
bubble fed by live useSessions lookup (drafts fall back to title + id).

* fix(web): dismiss rich composer chip tooltips on mouse leave

contenteditable pointerout/relatedTarget was flaky so tips stuck after
leaving the chip. Hit-test on pointermove, clear on prose/input/leave.

* fix(web): address cold-review Blocker/Majors on rich composer

Exclude peer e2e from default Playwright; force plain-text paste; restore
newline hard-stop in findActiveWord; fix root-anchored selection mapping
and nested-block serialize; cover with unit tests.

* chore: drop accidental .cursor files from rich-composer tip

* fix(web): close remaining cold-review gaps on rich composer

Drop absolute peer e2e tooling imports, prove chip→markdown send, and
harden paste/EOL/focus/tooltip/Enter edges before Meta rematerialize.

Co-authored-by: Cursor <cursoragent@cursor.com>

* chore: absorb soup playwright.config union for clean remat

Keep fork peer-stack timeouts/annotated-video wiring and add testIgnore
for e2e/peer so the next driver rematerialize does not conflict.

Co-authored-by: Cursor <cursoragent@cursor.com>

* revert: drop fork playwright tooling from upstreamable tip

Peer-stack annotated-video + HAPI_PEER wiring stay on fork main / soup.
Product tip only needs testIgnore for e2e/peer (see docs/tooling/peer-stack.md).

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(web): fix rich composer Shift+Enter double newline and paste space

Prefer manual newline+pad over execCommand insertLineBreak, and stop
applying autocomplete trailing-space on paste/drop paths.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(web): pad EOL Shift+Enter after Range.insertNode split

insertNode always leaves an empty text sibling, so !nextSibling never
saw EOL; detect meaningful trailing content and cover with jsdom tests.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(web): drop custom onDrop from rich composer

Intercepting drop without caretRangeFromPoint landed text at EOF or
no-oped in-editor moves. Native CE drop is enough for #1215; paste
still forces plain text.

Co-authored-by: Cursor <cursoragent@cursor.com>

* feat(web): sidebar-parity tooltips on rich composer session chips

Reuse SessionRowSummary (flavor, thinking/attention, schedule, todos,
relative ago, path) for chip hover so the tip matches the session list.

Co-authored-by: Cursor <cursoragent@cursor.com>

* chore: keep peer-stack e2e off the upstreamable tip

Peer specs and playwright.peer.config stay on fork main per
docs/tooling/peer-stack.md; default config still testIgnore's e2e/peer.

Co-authored-by: Cursor <cursoragent@cursor.com>

* feat: cite sessions with UUID wire + inspect_peer for agent/overseer

Rich composer chips already serialize to [title](/sessions/<id>); flush
before send so the agent prompt never gets title-only chip text. Add
inspect_peer (MCP + hapi inspect-peer) as the read twin of ping_peer so
that same id is immediately usable for overseer/agent peer lookup, with
system-prompt glue from citations to inspect/ping.

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(cli): gate inspect_peer behind permission approval

Cross-session history reads need the same prompt path as ping_peer:
keep inspect_peer off Claude --allowedTools and treat it as sensitive
in ACP/OpenCode read-only mode so prompt injection cannot silently
enumerate peer transcripts.

Co-authored-by: Cursor <cursoragent@cursor.com>

* chore: clarify playwright peer testIgnore is upstream-safe

Co-authored-by: Cursor <cursoragent@cursor.com>

* fix(web): keep session UUIDs on rich composer copy/cut/paste

Copy/cut write wire markdown so chips do not collapse to @title-only
clipboard text; paste reparses session links back into atoms.

Co-authored-by: Cursor <cursoragent@cursor.com>

---------

Co-authored-by: Cursor <cursoragent@cursor.com>

web/src/lib/sessionReference.ts

@@ -113,3 +113,60 @@ export function parseSessionPathHref(href: string): string | null {
         return null
     }
 }
+
+/** Live / fallback fields for composer mention chip hover tooltips. */
+export type SessionMentionTooltipSource = {
+    id: string
+    title: string
+    active: boolean
+    lifecycleState?: string | null
+    path?: string | null
+    worktreePath?: string | null
+    /** Preformatted relative time (sidebar "ago"), when available. */
+    relativeTime?: string | null
+    thinking?: boolean
+    /** Sidebar attention label (permission / input / unread / …). */
+    attentionLabel?: string | null
+}
+
+export type SessionMentionTooltipModel = {
+    title: string
+    lines: string[]
+    ariaLabel: string
+}
+
+/**
+ * Expand a truncated `@chip` into full title + meta for aria-label / fallback tip.
+ * Visual hover uses SessionRowSummary when a live SessionSummary is available.
+ */
+export function formatSessionMentionTooltip(
+    session: SessionMentionTooltipSource | null,
+    fallbackTitle: string,
+    id: string
+): SessionMentionTooltipModel {
+    const shortId = id.slice(0, 8)
+    const rawTitle = (session?.title || fallbackTitle || shortId).replace(/\s+/g, ' ').trim()
+    const title = rawTitle || shortId
+
+    let status: string | null = null
+    if (session) {
+        if (session.lifecycleState === 'archived') status = 'Archived'
+        else if (session.thinking) status = 'Thinking'
+        else if (session.attentionLabel) status = session.attentionLabel
+        else status = session.active ? 'Active' : 'Inactive'
+    }
+
+    const path = (session?.worktreePath || session?.path || '').trim() || null
+    const lines: string[] = [
+        status ? `Session · ${shortId} · ${status}` : `Session · ${shortId}`,
+    ]
+    const ago = session?.relativeTime?.trim()
+    if (ago) lines.push(ago)
+    if (path) lines.push(path)
+
+    return {
+        title,
+        lines,
+        ariaLabel: [title, ...lines].join('. '),
+    }
+}