feat(web,api): add Budget/Roles dashboard -- final phase of the harness redesign (Phase 9b)

Two new tabs, matching Phase 9a's conventions: Budget (per-provider spend
meters, escalation funnel, spend-over-time) and Roles (version history,
draft activation, readable escalation-ladder view) -- the human-facing
surface for the token-husbanding value proposition and the Phase 5/8
versioned role-config system.

New backend (minimal, additive, matching existing endpoint conventions --
unauthenticated like /api/budget and /api/roles/*):
- internal/storage/dashboard.go: QueryEscalationFunnel (executions grouped
  by escalation_rung + agent, count + cost) and QuerySpendTimeseries (cost
  per provider bucketed hourly/daily, mirroring QueryDashboardStats'
  existing bucketing expressions). Documented honestly: rung 0 is not
  exclusively "resolved locally" -- escalation_rung defaults to 0
  uniformly, so non-role-typed executions (which never climb a ladder)
  land there too, alongside role-typed tasks genuinely resolved at tier 0.
  A role-only variant would need a join against tasks.config_json with no
  queryable role column on executions -- intentionally out of scope.
- internal/api/dashboard.go: GET /api/escalation-funnel, GET
  /api/spend-timeseries (both ?window=5h|24h|7d|<duration>, default 24h).
- internal/storage.ListRoleNames + GET /api/roles: the "which roles exist"
  gap -- there was no way to discover role names before this, only to list
  versions for a role you already knew the name of.

Chart-form decisions (dataviz skill, invoked before writing chart code):
horizontal stacked bar for the escalation funnel (rung order already
encodes the funnel shape positionally; color only needed for per-provider
segments within each rung); multi-line for spend-over-time; a fixed-order
categorical palette from the skill's validated palette.md slots for
provider identity (re-validated against this app's dark surface, passing);
a separate status (good/warning/critical) palette for budget meters,
deliberately distinct from both --state-* and the provider palette. Caught
and fixed a real bug during visual QA: converging near-zero end-labels on
the spend chart were overlapping (an anti-pattern the skill explicitly
flags) -- fixed with a 14px minimum-gap check before direct-labeling an
endpoint, leaning on the legend/tooltip otherwise.

Verified with a real running server, real seeded data (65 executions across
rungs 0-2 with a realistic provider mix, 2 roles with active/draft/retired
role_configs versions written directly via internal/storage), and a real
headless-browser session (reusing Phase 9a's Chromium/proxy scaffinding):
confirmed correct rung totals/percentages, provider legends, a 3-line spend
chart, live window-selector re-render, correct active-version highlighting
on the role panel, and a real Activate click on a draft version -- verified
via both DOM re-render and a direct backend GET that it truly persisted.

go build/vet/test -race -count=1 all pass, full suite. node --test
web/test/*.mjs: 291/291 passing (16 new).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01V1moSNCJRcP6kykA4tyUSs

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