Upstream integration cycle: environment compatibility

[rynfar]

Continue the frozen upstream review through 6d1d549441be84f19696ab59ed7e2fbf305280d4 after #592. Maintainer explicitly authorized proceeding to remote-environment compatibility.

Bounded sources: 2c16c1d264173d86fc354e9a4c0c78cd42e514b7 (#11974), 935c55b3778fdeae0e25b250ce2a9fa7e79c0327 (#11990), c1b2ed6504bbd57440d03c6a5af2736f33be7c65 (#12026), 6ee03240bccd9287a8c2246e9547697aa5857998 (#12030). Review and adapt protocol compatibility checks, discovery gating, neutral unsupported presentation and stable machine icons as one behavior group.

Preserve Pylon protocol/product identity, remote authentication, pairing, relay/SSH routing, multi-environment ownership and reconnection. Trace the complete dependency chain before adoption; no new upstream fetch or global cursor advancement. Verify contracts/client runtime/server/web/mobile affected entry points and reverse transitions with focused tests and scoped checks. Existing browser authorization applies to isolated evidence capture. No release/install authorized. New PR merge requires approval and green checks.

[rynfar]

Added required dependency 2587c8060c103245b4f970b925977008f2592d1d (#11478): persisted saved-environment enabled state and off/on controls. Credentials/cache/config remain saved when off; remove remains a separate action. All five sources are integrated on upstream/2026-09-17-environment-compatibility in /tmp/pylon-environment-compatibility-20260917.

Pylon adaptations preserve connection layouts/edit controls, WSL ownership, branding and existing authentication parameters. Endpoint/profile equality ties compatibility to a saved connection without importing the unrelated GitHub-routing feature. Explicit retry rechecks a blocked direct environment after upgrade; resolver preflight still prevents an incompatible socket.

199 focused tests passed before the added direct-recovery regression; the registry suite with that regression passes (28 tests). Scoped typecheck fixes are in progress, followed by isolated web verification and evidence. No PR yet; no merge/release/install. #592 was merged at f3788ae8b26234cf1af63698247d419388bc6a2b with authorization and green checks; #591 closed.

[rynfar]

PR #595 is ready for review at f0b455f192 (environment compatibility and saved off-state). Browser evidence is uploaded: #595 (comment).

208 focused tests pass, with scoped contracts/client-runtime/web/mobile/desktop/server typechecks and changed-file lint. CI identified the existing mobile row test importing native appearance dependencies through the newly added switch; its native component fixture is now isolated and all eight affected tests pass. All final-head CI checks pass at f0b455f19264eebfa83ce3f8162b0fb1d2cf63f5; PR #595 is ready to merge after developer approval. No native rendered/live relay verification is claimed.

#592 merged at f3788ae8b26234cf1af63698247d419388bc6a2b. #595 is not merged; developer approval remains required. Frozen upstream head 6d1d549441be84f19696ab59ed7e2fbf305280d4 and review cursor bbedad0278bbf753503184c00e0c09a0eab6679c remain unchanged. Exact adopted sources are in this issue and PR. No release or install.

Next proposed dependency group after this lands: thread reading-position recovery, source f17165a76b1a782831eb6a05a4383b27283df15d (#12144), pending its bounded comparison.