[BUG] Markdown link labels never clickable in Orca/tmux — no OSC 8 emitted for unrecognized TERM_PROGRAM, FORCE_HYPERLINK=1 ignored

Bug Description

Markdown links ([label](url)) in assistant responses render as a styled label with no OSC 8 escape emitted, so the label is not clickable. Only bare URLs (linkified as plain text by the terminal itself) remain clickable. This happens whenever the terminal is not recognized — observed with TERM_PROGRAM=Orca (Orca embedded terminal) and TERM_PROGRAM=tmux (tmux inside Orca).

Setting FORCE_HYPERLINK=1 before launching has no effect (also noted in #72998, where the variable is ignored for the opposite purpose — disabling).

Steps to Reproduce

1. Run Claude Code inside a terminal whose TERM_PROGRAM is not on the capability allowlist — e.g. Orca (TERM_PROGRAM=Orca) or any tmux session (TERM_PROGRAM=tmux, TERM=tmux-256color).
2. Ask the assistant to print both forms:

• markdown: [example](https://example.com/some/long/path)
• bare URL: https://example.com/some/long/path

1. Observe: the markdown label renders styled but is not clickable (no OSC 8 region, nothing on hover); the bare URL is clickable only because the terminal itself linkifies plain-text URLs.
2. FORCE_HYPERLINK=1 claude — behavior unchanged.

Why the terminal is not the problem

| Layer | OSC 8 support | Evidence |
|---|---|---|
| Orca terminal | ✅ renders OSC 8 | stablyai/orca#6880 (test matrix in issue body: "rendered, clickable, URL hidden") |
| tmux 3.7b | ✅ supports the hyperlinks terminal-feature | binary contains the feature and Hls=\E]8;...; passthrough needs set -as terminal-features ",*:hyperlinks" |
| Claude Code renderer | ❌ no OSC 8 emitted for markdown labels | this report |

So in the direct-Orca case the chain is known-good end to end, yet no OSC 8 arrives; in the tmux case the user can open the tmux side with one config line, but that is moot while nothing is emitted upstream.

Expected

Either of:

• honor FORCE_HYPERLINK=1 as an explicit user override of terminal capability detection (matching the supports-hyperlinks ecosystem convention), and/or
• treat TERM_PROGRAM=tmux (tmux ≥ 3.4 supports the hyperlinks feature) and TERM_PROGRAM=Orca as hyperlink-capable.

The TERM_PROGRAM allowlist approach can never see through tmux nesting (the outer terminal's identity is not visible inside), so an env-var override is the only mechanism that works for every setup.

Related: #79839 (file-path OSC 8 regression in assistant responses), #72998 (FORCE_HYPERLINK ignored for disabling), #13008 / #77576 (file-path hyperlink requests), stablyai/orca#6880 (terminal-capability detectability for agent TUIs).

Environment Info

• Platform: macOS 26.5.2
• Terminal: Orca (embedded terminal, TERM_PROGRAM=Orca) and tmux 3.7b inside Orca (TERM_PROGRAM=tmux, TERM=tmux-256color)
• Version: 2.1.220