feat(templates): auto-discover flowfile templates on sync

[jahvon]

Summary

Flowfile templates previously had to be registered by name (flow template add) in the global config to be usable by name. This PR makes them auto-discovered from *.flow.tmpl files within workspaces during flow sync — the same way executables (.flow files) are found — so dropping a template into a workspace makes it available with zero configuration.

Registration still works and is preserved for templates that live outside a workspace or should be available from every workspace.

Resolution order: -f <path> → registered name → discovered name.

What changed

• Shared discovery walk (pkg/filesystem/executables.go): extracted the workspace tree walk into a shared findFiles(cfg, filter, match); executable discovery is behavior-preserving.
• Template loader (pkg/filesystem/templates.go): LoadWorkspaceFlowFileTemplates, mirroring the executable loader.
• TemplateCache (pkg/cache/templates_cache.go): mirrors ExecutableCacheImpl — validates each template, warns on cross-workspace name collisions, persists to the store. Added as a third stage in cache.UpdateAll, so flow sync discovers templates.
• App context (pkg/context/context.go): Context.TemplateCache constructed and propagated in ShallowCopy.
• Command wiring (cmd/internal/): name resolution falls back to the cache; template list merges registered + discovered (registered wins on collision); template add now stores absolute paths.
• Workspace-scoped filter (types/workspace/schema.yaml): a templates include/exclude block in flow.yaml, same semantics as executables.
• Docs: updated the templating guide with an auto-discovery section, scoping, and collision handling.
• Fixes: canonicalized .tmpl.flow → .flow.tmpl in test fixtures.

Only files with the exact .flow.tmpl extension are discovered, so artifact partials like deployment.yaml.tmpl are never treated as template generators. For cross-workspace name collisions, a workspace/name reference disambiguates.

Testing

• Unit: cache (discovery, invalid-skip, dup-warn, qualified resolution), filesystem discovery (extension matching + exclusions), mergeTemplates precedence.
• E2E: seed an unregistered .flow.tmpl, flow sync, then list and generate it.
• flow validate passes (generate → lint → unit + e2e → schemas).

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 71.91011% with 50 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
pkg/cache/templates_cache.go	69.72%	19 Missing and 14 partials ⚠️
pkg/filesystem/templates.go	60.00%	6 Missing and 2 partials ⚠️
cmd/internal/template.go	84.00%	3 Missing and 1 partial ⚠️
pkg/context/context.go	0.00%	3 Missing ⚠️
pkg/cache/cache.go	33.33%	1 Missing and 1 partial ⚠️

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