[web] Positions view: per-tranche MTM, stop distance, bracket status, freshness and attestation chips

[eaitbrahim]

Context (verified)

• positions stores one row per tranche: qty, entry_fill, entry_fee, initial_stop, partial-exit accumulators (realized_qty/realized_proceeds/realized_fees), bracket_order_id, status (keel/data/db.py).
• The agent computes mark-to-market equity per cycle (agent._mark_to_market_equity, keel/agent/agent.py:404) — the last mark per product needs exposing, not recomputing client-side.
• Freshness already has a human-readable entry-gate vocabulary: missing / behind / unconfirmed (keel/data/freshness.py:151-262, entry_bar_ready) — currently buried in Status rows.
• asset_attestations (v6) and instrument_attestations (v10) tables exist with screen_exceptions; the quarterly-expiry semantics match the pinned-quarterly-snapshot decision recorded on keel-broker-alpaca Phase B: equities paper profile, attestation semantics, runbook #370.

Today Positions is a table inside Status. Alpaca's Positions page (avg entry, current price, market value, unrealized P&L, per-row close) is the skeleton — minus its one-click close, which is refused.

Scope

1. Positions view (Portfolio section): rows grouped by product, one disclosure per tranche:
   • entry fill and entry fee, current price, unrealized P&L (server-computed off the agent's mark, Field wire contract), realized-to-date on partial exits
   • initial-stop distance (% and price), bracket status (resting / filled / cleared)
2. Freshness chip per product rendering the real entry_bar_ready verdict (missing/behind/unconfirmed) — the gate outcome, not just data age. Finer than any broker's "as of" stamp.
3. Attestation chip per product: Attested: Q2-2026 · Purif: 0.38% → RE-ATTESTATION REQUIRED (warn state) when the quarterly filing window expires or a ratio breaches. Reads the existing attestation tables; forward-compatible with keel-broker-alpaca Phase B: equities paper profile, attestation semantics, runbook #370's XBRL screening fields, which render in the same chip when present.

Refusals

• No close button. Ever. Exits degrade to typed-phrase friction, never a table-row tap — a panic tap must never be the last line of defense.
• Zero client-side math.

Acceptance

• MTM P&L reconciles with the equity figure driving the drawdown rails (same mark, one source of truth).
• Chips render warn states correctly on synthetic expired/breached attestations.
• No monetary JSON numbers; sortable columns declared server-side.

Depends on #698 (mark source) and the Orders view payload patterns (Sprint 1, third).