fix(install.ps1): anchor cosign identity to version tags (parity with #415)

[LukasWodka]

Bugbot on promotion PR #419, confirmed real: #415 anchored install.sh's cosign identity to @refs/tags/v.* (and release.yml's verification doc with it) but install.ps1 still accepted @.* — Windows trusted signatures from non-tag workflow runs that Unix correctly rejects. This applies the same anchor to install.ps1 (covers v*-rc.N staging tags identically).

🤖 Generated with Claude Code

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Note

Low Risk
Single-line installer hardening that narrows accepted cosign identities; no runtime or auth changes.

Overview
Aligns Windows cosign verification in install.ps1 with the stricter policy already used in install.sh.

The --certificate-identity-regexp for release.yml is tightened from @.* to @refs/tags/v.*, so signatures are only accepted when the workflow identity is tied to a version tag (including v*-rc.N staging tags), not arbitrary workflow refs.

^{Reviewed by Cursor Bugbot for commit f4c5640. Bugbot is set up for automated code reviews on this repo. Configure here.}

[LukasWodka]

👋 Heads-up — Code review queue is at 44 / 30

Above the WIP limit. The team convention is to review existing PRs before opening new work.

Open PRs currently in Code review (oldest first):

• averaging-service#219 — release-train: develop -> staging · author: @LukasWodka · no reviewer assigned
• averaging-service#220 — ci: code-quality caller (advisory) · author: @LukasWodka · no reviewer assigned
• backend#1201 — docs(rfc): Data spaces & federated dataset composition (draft) · author: @LukasWodka · reviewer: @saadqbal
• backend#1217 — docs(rfc): Dataset integrity & score reproducibility (draft) · author: @LukasWodka · reviewer: @saadqbal
• backend#1261 — RFC-BACKEND-0008: board & process reset (decision RFC — for markup) · author: @LukasWodka · reviewer: @saadqbal
• backend#1284 — docs(deploy): backend deploy runbook skeleton (#1263) · author: @LukasWodka · no reviewer assigned
• backend#1293 — fix(heartbeat): tolerate unknown experiment_key in training_info (#1287) · author: @divyasinghds · no reviewer assigned
• backend#1297 — feat(db): gate MSSQL-only ODBC driver per engine + add psycopg (#1164) · author: @saadqbal · no reviewer assigned
• backend#1298 — fix(guardrails): reuse existing dimensional anomaly monitor (#1160) · author: @saadqbal · no reviewer assigned
• backend#1299 — release-train: develop -> staging · author: @LukasWodka · reviewer: @saadqbal

Pull from review before opening new work. (This is a nudge from the kanban WIP check, not a block.)

[shujaatTracebloc]

LGTM — verified.

Correctness: The one-line change makes install.ps1 an exact mirror of install.sh:364 — both now use release.yml@refs/tags/v.*. This closes the platform gap where Windows accepted cosign signatures from the release.yml workflow running on any ref (branches, arbitrary tags), which Unix already rejected.

Staging tags:refs/tags/v.* correctly matches v*-rc.N staging tags (e.g. refs/tags/v1.2.3-rc.1), so promotion/staging installs keep working.

Scope:install.ps1 has exactly one --certificate-identity-regexp; no other unanchored @.* patterns remain.

CI: all checks green (e2e jobs correctly skipped — no e2e-relevant changes), Cursor Bugbot clean, no unresolved review threads.

[LukasWodka]

/fr-pass