TEMPLATE_MANIFEST references Rai-charter.md but file is rai-charter.md (masked by macOS case-insensitivity) #1971

Summary

TEMPLATE_MANIFEST declares source: 'Rai-charter.md' (packages/squad-cli/src/cli/core/templates.ts:139-140), but the file on disk is rai-charter.md (lowercase) in all four template locations. It is the only one of 59 manifest sources that does not resolve case-sensitively.

Found while fixing the README casing in #1949; deliberately left out of that docs PR because the fix spans runtime code, tests, and a prompt template.

Why this hasn't been caught

existsSync gives a false pass on macOS, because the filesystem is case-insensitive. A check that reads directory entries and compares exact basenames tells the truth:

total 59  case-sensitively missing 1
  MISSING: Rai-charter.md

On disk, all four locations agree:

.squad-templates                 charter.md fact-checker-charter.md rai-charter.md scribe-charter.md
templates                        charter.md fact-checker-charter.md personal-charter.md rai-charter.md scribe-charter.md
packages/squad-cli/templates     charter.md fact-checker-charter.md rai-charter.md scribe-charter.md
packages/squad-sdk/templates     charter.md fact-checker-charter.md rai-charter.md scribe-charter.md

This is exactly the failure mode the codebase already warns about in its own comment at packages/squad-sdk/src/config/init.ts:1141-1151 — mixed-case lookups missing on case-sensitive filesystems (Linux CI), referencing the regression #1299 was fixing.

Blast radius

The wrong casing is load-bearing in several places, which is why this needs its own PR:

• packages/squad-cli/src/cli/core/templates.ts:139-140 — manifest source and destination
• packages/squad-cli/src/cli/core/upgrade.ts:1027 — { dirName: 'Rai', templateFile: 'Rai-charter.md' }
• test/template-routing.test.ts:61 — currently pins the incorrect mapping, so it will need updating in the same change
• packages/squad-cli/templates/squad.agent.md.template:912 — runtime prompt instructs reading .squad/templates/Rai-charter.md
• .squad/skills/coordinator-init-mode/SKILL.md:76 — prose reference

Note the destination directory agents/Rai/charter.md is intentionally capitalized (dirName: 'Rai') and should stay that way — only the source filename is wrong.

Suggested durable fix

Add a guard asserting every manifest source exists case-sensitively (read readdirSync entries, compare exact basenames — do not use existsSync, which is what let this through). That single test would have caught this and prevents recurrence across all 59 entries.

I considered adding that guard in #1949 but it would have failed on this pre-existing entry and required an allowlist, so it belongs here with the fix.

Acceptance criteria

• Manifest source corrected to rai-charter.md
• upgrade.ts:1027 templateFile corrected
• test/template-routing.test.ts updated to pin the correct mapping
• Prompt template and skill prose references corrected
• Guard test added: every TEMPLATE_MANIFEST source resolves case-sensitively (not via existsSync)
• Verified on a case-sensitive filesystem (Linux CI), not just macOS