Harden agent CLI startup in fragile user environments

[baron]

Context

This started as an investigation into slow/stuck Codex connection startup, but the root theme is broader: agent CLIs can fail or stall when RepoPrompt is launched from a macOS app environment that does not match the user's terminal PATH, shell aliases, Homebrew/Fish setup, or legacy MCP/CLI symlink state.

This PR hardens that startup boundary without abandoning the legacy path behavior users may already depend on.

Summary

• make optional Codex app-server memory-mode setup best-effort so it cannot block session readiness
• move CE user-space CLI links to the no-space ~/RepoPrompt path for newly generated configs/installs
• grandfather legacy CE Application Support links, older Classic-style CLI names, and existing managed app-bundle destinations as repairable/recognized paths
• improve OpenCode/Cursor executable discovery diagnostics for app-launched PATH environments by reporting candidates and fallback-env hints
• add a Claude wrapper fallback for local/alias-only installs at ~/.claude/local/claude
• add coarse Sentry breadcrumb/metric coverage for CLI path resolution failures without reporting raw filesystem paths

Why this shape

• Codex was the trigger, but PATH/env fragility is the cross-provider failure mode.
• The no-space ~/RepoPrompt path improves generated config robustness going forward.
• Legacy paths remain explicitly supported so existing users are not stranded by a cleaner default.
• Diagnostics now aim to explain "works in Terminal, fails in app" instead of collapsing everything to "CLI not found."

Validation

• make dev-test FILTER=OpenCodeACPLaunchResolverTests
• make dev-test FILTER=CursorACPLaunchResolverTests
• make dev-test FILTER=CECLINamingAndRoutingTests
• make dev-test FILTER=CLIPathInstallerTests
• make dev-test FILTER=DebugCLIInstallerScriptTests
• make dev-format
• make dev-lint
• python3 Scripts/test_suite_optimizer.py verify-ledger --ledger Scripts/Fixtures/test-suite-contract-ledger.tsv
• .agents/skills/rpce-contribution-check/scripts/preflight.sh commit
• .agents/skills/rpce-contribution-check/scripts/preflight.sh push

Notes

• Sentry telemetry records provider kind, shell environment source, and candidate count only; raw paths stay out of telemetry.
• This does not attempt the larger path-doctor UX or worktree artifact pathing fixes; those remain separate follow-ups.