fix(examples): strategy evolution author takes BRIDGE_CWD

[drewstone]

Problem

The strategy-evolution example's live author path failed before the model ran.
A cli-bridge process runs a turn in its own working directory unless the request names one.
A bridge started inside its checkout therefore runs the author in a directory that already holds a CLAUDE.md.
The author profile writes its instructions to CLAUDE.md and refuses to replace a different file, so the bridge refused the turn.

Change

• examples/strategy-evolution/strategy-evolution.ts: the bridge executor takes cwd from BRIDGE_CWD, an empty directory on the bridge host.
• examples/strategy-evolution/README.md: documents BRIDGE_CWD, and the sample output shows the interval Eval 0.199 computes ([0.195, 0.350]; the published 0.282.0 and this branch both compute an upper bound of 0.34985).

The offline path is unchanged.

Proof (real runs, drew-gtr-pro, author through a Mac cli-bridge over an SSH tunnel)

Offline, from this branch: pnpm exec tsx examples/strategy-evolution/strategy-evolution.ts .evolution-cwd-offline

  carry-forward            selected  parent sample selection Δ +0.284 on 12 tasks
claim: ship (finalist node_fe43aed7c3028f91b481f9e1ac691e66 beat the root on the 24 test units at confidence 0.95 (1 finalist, family-wise 0.95))
test lift 0.276 [0.195, 0.350] on 24 tasks
spend: $0.0054 known

Live author, AUTHOR_MODEL=claude-code/sonnet, without BRIDGE_CWD (the bridge runs in ~/code/cli-bridge):

Error: strategy author failed: bridgeExecutor: bridge stream error: AgentProfile workspace materialization failed: Refusing to replace existing workspace file: CLAUDE.md — planned sha256:7fdb9d7a… != existing sha256:f20d30c7…

f20d30c7… is the sha256 of ~/code/cli-bridge/CLAUDE.md.

The same run with BRIDGE_CWD set to an empty directory gets past materialization (the directory now holds CLAUDE.md with sha256 7fdb9d7a…, the planned file), and the turn completes:

Error: strategy author: Runtime turn did not report the model actually used; refusing to label the response with the requested model

Both searches pause with the failure recorded as operation-recorded (proposer-error) and resume from their ledgers.

Still open (not this PR)

A live author still cannot finish through cli-bridge: no backend on the checked bridges reports its served model.
The streamed chunks carry only the requested id (claude-code/sonnet, kimi-code/kimi-for-coding), and Runtime's profileChatClient refuses an unreported model by design.
Claude Code reports the served model in its stream-json output (init.model = claude-sonnet-5, also on each assistant message).
cli-bridge's claude backend reads only session_id from the init event (src/backends/claude.ts, the subtype === 'init' branch), although ChatDelta.model and the SSE writer already carry a served model.
Emitting it changes behavior for every Runtime bridge worker that declares an alias such as sonnet, because bridgeExecutor rejects a reported model that differs from the declared one, so it needs its own change with that migration.