fix(client): session jump must navigate through uiWorkspace, not the removed sessions.open

[Fishsb]

Problem

On every dsh runtime since 0.1.6 (including the current 0.1.7-rc.2), the 🤖 跳转会话 ↗ button and the session-jump affordances on cards, chips, and execution rows do nothing. The click reports:

会话导航不可用，会话 ID：<id>

…even though the session is live and visible in the sidebar.

Root cause

src/client/session-jump.ts resolves the runtime sessions service and calls sessions.open(id). That selector no longer exists: the ISessions contract in 0.1.7-rc.2 states

Host catalog and local reference-source counts; navigation belongs to view owners.

Verified across releases:

@deepseek-ai/dsh-api-session-controller	ISessions.open(id)
0.1.5-rc.2	present — open(id: SessionId): void ("Select a session as current.")
0.1.6-alpha.2	removed
0.1.7-rc.1	removed
0.1.7-rc.2	removed

Reading a method the service no longer ships yields undefined, and calling it throws. The jumper's own try { … } catch { return 'unavailable' } then swallows the TypeError into a bare "navigation unavailable" verdict — so the removal degraded silently instead of failing loud.

The supported navigation entry is uiWorkspace.openSession(target) ("Select a Session and show its Conversation as one UI navigation action").

Fix

Resolve the navigation entry structurally instead of assuming a method exists:

const navigate = (sessions, sessionId) => {
  const nav = access.getUiWorkspace?.()
  if (typeof nav?.openSession === 'function') { nav.openSession(sessionId); return true }  // 0.1.6+
  if (typeof sessions.open === 'function')    { sessions.open(sessionId);    return true }  // 0.1.5 and older
  return false
}
// …
return navigate(sessions, sessionId) ? 'opened' : 'unavailable'

• SessionsServiceFace.open is now optional, and getUiWorkspace is an optional accessor, so existing callers (and the existing tests that inject only two accessors) keep compiling. The legacy path is retained for older runtimes rather than dropped.
• unavailable now means "this runtime provides no navigation entry" — a real verdict, not a swallowed exception.
• Accessors stay lazy/per-click (unchanged rationale: a service provided after apply must not be captured as undefined).
• lib/client.js rebuilt.

Verification

• Red → green: the new regression test drives the jumper against a runtime-shaped sessions service that has no open key at all. Before the fix it fails with expected 'unavailable' to be 'opened'; after, it passes.
• npm test: 352/352 pass (24 files). tsc --noEmit clean.
• npm ci && npm run build && npm test (the CI pipeline) run on a clean clone: build reproduces the committed lib/client.js byte-for-byte, leaves the tree clean, tests green.
• Committed bundle delta vs main proven to be exactly two edits — the navigate() helper and the third accessor at the call site — nothing incidental.
• End-to-end against a live host: the bundle the running dsh web server actually serves was fetched over HTTP, the jumper function extracted, and exercised against both runtime shapes (0.1.7: no open, uiWorkspace present → opens; legacy: sessions.open only → opens) plus the archived/missing/unavailable verdicts.

Note for older runtimes

The legacy sessions.open branch is deliberately kept, so this fix is additive for 0.1.5-era hosts and is not a breaking change for the dshReleases compatibility matrix.