refactor(ci): split the issue analyst out and brief the review job from a file

The issue analyst moves verbatim from claude-bot.yml into its own
claude-issue-analyst.yml, so claude-bot.yml now holds only the pull-request
side: review, @claude mentions and conflict resolution.

The review job's briefing was a single 2,600-character quoted string inside
claude_args, unreadable and unreviewable. It now lives in
.github/claude/review-job.md, assembled at run time with a "This run"
section that hands the reviewer the pinned head SHA, the pull request and
the exact check-runs command, and reaches the CLI through
--append-system-prompt-file. The agent-mode action sets no system-prompt
append of its own, so the file flag cannot collide with one.

Findings no longer carry the fix: REVIEW.md and the brief both forbid
suggestion blocks, patches and replacement snippets, overriding the
code-review skill's --comment step, which attaches a committable suggestion
to any small fix. A finding states what is wrong, where, what triggers it
and what breaks; the maintainer decides the change.

bot_context_test.go

@@ -1,9 +1,7 @@
 package main
 
-// The Claude bot prompts in .github/workflows/claude-bot.yml no longer restate
-// repository facts; they read .github/claude/repo-context.md instead. A stale
-// claim in that file is invisible until it produces a wrong review, so every
-// claim a machine can check is pinned here.
+// The bot prompts under .github/workflows/ read .github/claude/repo-context.md
+// instead of restating repo facts; a stale claim there is invisible, so pin it.
 
 import (
 	"os"