#565 Managed skills ship with dangling reference-doc links

Description

swamp repo upgrade (version 20260605.000321.0) installs managed skills whose SKILL.md files link to reference docs that are not bundled in the release. The links resolve to nonexistent files, so any agent (or human) that follows them hits a dead end. This is self-evident in the swamp-issue skill itself, whose documented sanitize/version-check states point at missing files.

Affects both the .claude/ and .agents/ skill trees identically.

Missing files

swamp-issue/references/ (present: formatting.md, output_shapes.md):

• sanitization.md — linked from SKILL.md lines 85, 170, 226 and references/formatting.md line 6
• version_check.md — linked from SKILL.md line 186 (the version_check state of the bug-report workflow)

swamp-report/references/ (present: report-types.md, testing.md):

• control-model.md — linked from SKILL.md lines 72, 180
• filtering.md — linked from SKILL.md lines 73, 182

Steps to reproduce

1. In a swamp-managed repo, run swamp repo upgrade to version 20260605.000321.0.
2. Open .claude/skills/swamp-issue/SKILL.md and follow the link to references/sanitization.md.
3. The target file does not exist under references/ (only formatting.md and output_shapes.md are shipped).
4. Same for version_check.md, and for control-model.md / filtering.md in the swamp-report skill.

Expected

Either the four reference docs are bundled with the skills, or the SKILL.md files do not link to them.

Actual

The docs are referenced but absent, breaking the documented workflows (notably the swamp-issue bug-report state machine, which instructs the agent to read sanitization.md and version_check.md).

Environment

• swamp 20260605.000321.0
• Detected via GitHub Copilot review on a routine upgrade PR; confirmed by filesystem check in both .claude/ and .agents/ trees.