refactor(refs): condense language-agent references to local knowledge (W-PR2)

[notque]

Track W, PR2 of 7. Remediates the 89:11 generic-to-local ratio for the four language agents. Per the mandate, this merges and condenses — every agent keeps its references/ dir and at least one file. No agent deleted.

Measured

Agent	Before	After	Cut
python-general-engineer	10,005 w / 12 files	1,456 w / 2 files	85%
golang-general-engineer	11,793 w / 10 files	1,217 w / 2 files	90%
golang-general-engineer-compact	3,183 w / 3 files	545 w / 1 file	83%
php-general-engineer	4,581 w / 4 files	1,638 w / 2 files	64%
Total	29,562 w / 29 files	4,856 w / 7 files	84%

Agent-references corpus: 225,511 -> 200,805 words.

Cut

Public-docs restatements a frontier model has cold: the python-errors exception catalog, Go concurrency/testing/security tutorials, the PHP security tutorial, gopls workflow narration, motivational preamble, and placeholder-entity examples.

Preserved (local knowledge, the actual asset)

• flask-jinja-webapp.md mode-600 -> nginx 403 incident, verbatim, plus the gunicorn template-cache restart rule and CSRF blueprint-exemption pins
• reddit_mod.py except OSError: pass silent-failure gate
• Peewee E712 ruff exception; host venv/pip mismatch rule
• GOMODCACHE library-source verification rule; rebuilt-binary stat staleness check; hermes/log-router dead-code A/B result; Go 1.18-1.26 version idiom tables
• PHP PostToolUse hook block, SAP Commerce context, hard gates

Defects fixed in passing

• python-modern-features.md shipped curl -LsSf https://astral.sh/uv/install.sh | sh — violates the home CLAUDE.md installer policy. Replaced with a pipx/pip path.
• php-security.md justified PHP prepared statements by citing Sequelize CVE-2023-25813, a Node ORM CVE. Bogus citation dropped. (The correct Node-context citation in reviewer-system is untouched.)
• php loading table rows 1-3 carried file links in the Signal column; keyword signals restored.
• golang-general-engineer-compact listed go-patterns twice in Companion Skills; merged to one row.

Gates (local, ruff 0.15.12 matching CI)

ruff check pass - ruff format --check 583 files pass - validate-references.py --check-do-framing pass - --check-placeholders pass - validate_reference_loading_tables.py exit 0 - pytest scripts/tests/ -q 4735 passed, 1 skipped, 139 xfailed.

--all structure issues improve 7 agents/15 issues -> 5/10; all residual flags are NO_CODE_EXAMPLES advisories on agents this PR does not touch.

Pruned 2 now-deleted entries from _KNOWN_OVERSIZED_SKILL_REFS (go-errors.md, python-preferred-patterns.md), per the same-PR rule.

Note, out of scope

agents/INDEX.json drift warning (43 indexed vs 44 .md on disk) is pre-existing on main and a false positive: base-instructions.md is a shared include, correctly excluded by the generator while the hook counts raw files.