fix(ci): harden agent issue prompts

[devi-labs]

Description

Harden the agent issue workflows so untrusted issue titles are no longer interpolated directly into workflow prompts. The workflows now pass only the issue number, require the agent to fetch issue details explicitly, treat issue content as untrusted data, and apply the paranoid-path block-mode headers to both triage and fix paths.

Reviewers' hat-rack 🎩

Please focus on the GitHub Actions trigger conditions and prompt boundaries:

• no direct interpolation of issue title/body into prompts
• the labeled trigger guard for trusted issue authors
• block-mode proxy headers on both agent workflows
• skill guidance for treating issue content as untrusted data

Screenshots or videos

N/A

Test plan

• Parsed both modified workflow YAML files with Ruby YAML loader
• Searched modified workflows for direct github.event.issue.title interpolation
• Verified agent-fix.yml now has paranoid-path block-mode headers
• Workflow dry run in GitHub Actions (not run: workflows are label-triggered and do not define workflow_dispatch; YAML parsing and PR CI were used instead)

[devi-labs]

Pushed follow-up commit 14e2f49 to tighten the labeled triggers and clarify the issue-number prompt handling

Validation done:

• Parsed both modified workflow YAML files locally with Ruby YAML loader.
• Confirmed there are still no direct github.event.issue.title / github.event.issue.body interpolations in the agent workflows.
• PR CI reran on the latest commit. The iOS e2e job is still failing before tests execute because Homebrew refuses the wix/brew tap for applesimutils

Refusing to load formula wix/brew/applesimutils from untrusted tap wix/brew.\nRun `brew trust --formula wix/brew/applesimutils` or `brew trust wix/brew` to trust it. - That failure appears unrelated to these workflow prompt-boundary changes.