fix(shared): handle PR links for local filesystem remotes

[rynfar]

A thread with saved PR links and an absolute filesystem Git remote can throw during legacy PR-link projection because it has neither a provider nor a hostname. Return no legacy link when the resolved host is absent, leaving the modern link array intact.

Adopts every hunk of 38f3c62304bfe79ea6c9f75a17afb732b555f48d (T3 #13463), in the separately frozen successor inventory for #865. The source commit retains attribution; its new test uses Pylon's branded ProjectId constructor. The shared helper is called by metadata decisions, event projection and SQL snapshot reads. Those consumers serve web, desktop and mobile across local, remote and tunnel connections. Existing Azure and Forgejo routing is retained; no schema, migration or provider capability changes.

Validation: the new regression fails before the fix with TypeError: Cannot read properties of undefined (reading 'toLowerCase') and passes afterward. All 54 focused thread-PR and source-control tests pass, including Hermes array-method compatibility and Azure/Forgejo identities. Shared typecheck, scoped lint, format and diff checks pass. Lint reports one existing reverse-method warning on the intentionally retained Hermes-compatible implementation; typecheck reports existing Effect suggestions. No live server or client runtime was exercised.

Related tracking: #865. Pending approved merge; original cycle bounds and cursor remain unchanged.

Model: GPT-6 (Codex). Harness: Codex in Pylon.

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	14.0 KiB	13.9 KiB	−35 B (−0.2%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.3 KiB	7.3 KiB	+6 B (+0.1%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.7 KiB	6.7 KiB	−41 B (−0.6%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	58.0 KiB	58.0 KiB	−44 B (−0.1%)	66.4 KiB	✅
Codex	Live turn messages	9	8	−1 (−11.1%)	21	✅
Claude	Total thread wire	14.0 KiB	14.0 KiB	−32 B (−0.2%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.3 KiB	7.3 KiB	0 B (0.0%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.7 KiB	6.7 KiB	−32 B (−0.5%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	58.9 KiB	58.8 KiB	−44 B (−0.1%)	66.4 KiB	✅
Claude	Live turn messages	9	8	−1 (−11.1%)	21	✅

Baseline: 95ab96b · PR result: a00ef91 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 115.7 KiB
• Claude decoded thread snapshot: 116.4 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.