fix(signal): avoid duplicate signal-cli missing note

[RomneyDa]

What Problem This Solves

Signal QuickStart could show two consecutive missing-binary notes after signal-cli installation failed: first the installer failure from the Signal prepare step, then the generic cliPath help note before asking for signal-cli path.

Why This Change Was Made

The path prompt itself is already the recovery action, and the installer failure already explains the failure. Removing the Signal-specific cliPath help note keeps the setup flow to one error note plus the path prompt without adding wizard state or changing shared setup behavior.

User Impact

Users see one Signal install failure message instead of two similar Signal missing-binary messages, then can still enter a custom signal-cli path.

Evidence

• pnpm test extensions/signal/src/core.test.ts -- --reporter=verbose
• pnpm exec oxfmt --check --threads=1 extensions/signal/src/setup-core.ts extensions/signal/src/core.test.ts
• git diff --check
• node scripts/run-oxlint.mjs --tsconfig config/tsconfig/oxlint.extensions.json extensions/signal/src/setup-core.ts extensions/signal/src/core.test.ts
• pnpm tsgo:extensions
• pnpm tsgo:extensions:test
• pnpm check:changed -- extensions/signal/src/setup-core.ts extensions/signal/src/core.test.ts via Blacksmith Testbox tbx_01kw12d6xprcv4gw3c8hb6pwg6
• .agents/skills/autoreview/scripts/autoreview --mode local --prompt "Review this focused OpenClaw Signal setup copy fix. Scope: avoid duplicate Signal missing-binary notes by removing the generic Signal cliPath help note; installer failure remains and the path prompt still appears. Touched files: extensions/signal/src/setup-core.ts and extensions/signal/src/core.test.ts. Focus on setup UX, wizard behavior, and test value."

[clawsweeper]

ClawSweeper status: review started.

I am starting a fresh review of this pull request: fix(signal): avoid duplicate signal-cli missing note This is item 1/1 in the current shard. Shard 0/1.

This placeholder means the worker is alive and reading the current context. I will edit this same comment with the actual review when the claws are done clicking.

Crustacean status: shell secured, claws on keyboard, evidence pebbles being sorted.