v0.0.13

Small cleanup release. Two low-risk items that had drifted since
v0.0.8 (SECURITY.md) and v0.0.11 (SKILL.md alias list).

Changed:

• EFFORT_TO_MODEL (PR #47): medium → claude-sonnet-4.6 (was
  claude-sonnet-4.5). Same Anthropic billing tier, no
  cost/quota impact on --effort medium flows. EFFORT_FALLBACK_CHAIN
  first-fallback entry for high / xhigh bumped to
  claude-sonnet-4.6 to stay consistent with the primary.
• Unchanged — --effort high / xhigh stays on
  claude-opus-4.6. The v0.0.12 opus alias bumped to 4.7 for
  users who explicitly type --model opus, but the effort-default
  intentionally holds on 4.6 to avoid the 7.5x opus-4.7 premium-
  request multiplier (through 2026-04-30) silently hitting
  automation.
• plugins/copilot/agents/copilot-rescue.md and
  plugins/copilot/skills/copilot-cli-runtime/SKILL.md had stale
  alias lists (still showed opus → 4.6, sonnet → 4.5, didn't
  list the v0.0.11 gpt / codex aliases). Refreshed to the
  v0.0.12 state + the v0.0.13 sonnet default.
• SECURITY.md (PR #46): threat model refresh for everything
  shipped since v0.0.3/4. Adds two bullets to "What the plugin IS
  designed to defend against" — concurrent-session broker hijack
  (v0.0.8 broker.lock + stale-PID recovery) and silent acceptance
  of malformed structured review output (v0.0.8/9 schema
  validator). Adds broker.lock to the Secrets and paths table.
  Expands "Known limits" to explicitly list per-ACP-session
  sandboxing and Windows review-path --effort as upstream-
  blocked rather than plugin-side plans.

Test suite: 153 tests, unchanged count (the sonnet bump is a
surgical rename, not new coverage). 152 pass, 1 skipped, 0 fail.
CI green on both Linux and Windows.

See merged PRs #46, #47 for the full review history.