docs: refresh planner queue for 4081

[asim]

Summary:

• Removed completed quickstart on-ramp item Keep website quickstart on the first-agent on-ramp #4071 from the autonomous planner queue.
• Promoted install troubleshooting Add install troubleshooting to the first-agent on-ramp #4077 as the next developer-adoption priority.

Assessment:

• Shipped: Align website quickstart first-agent on-ramp #4080 aligned the website Quick Start with the first-agent on-ramp and closed Keep website quickstart on the first-agent on-ramp #4071. Recent merged codex work also tightened examples/docs wayfinding and CLI agent-demo affordances.
• In flight: blog: draft v6.3.15 update #4022 is an open codex blog draft; it is narrative/content work and does not block the ranked implementation queue.
• Open queue: Add install troubleshooting to the first-agent on-ramp #4077 remains the only open codex enhancement issue and directly addresses install friction before the first-agent path.
• Top risk/gap: the on-ramp now explains scaffold/run/chat/inspect better, but install recovery is still not linked into the canonical path; that can strand new users before they reach micro agent demo or no-secret examples.
• Ranking rationale: the North Star and canon emphasize making agents feel like services on one runtime, and the current goal weights developer adoption at least as highly as hardening. With quickstart drift resolved, install troubleshooting is the highest-value next adoption seam.

Testing:

• PASS: go test ./internal/harness/zero-to-hero-ci -run TestFirstAgentWayfindingDocs -count=1
• WARNING: go test ./... timed out after 120s; client/grpc loopback tests failed under the environment proxy with "Loopback targets forbidden" before timeout.
• WARNING: golangci-lint run ./... timed out after 120s.

Closes #4081