docs: name what is blocked instead of a blanket fail-closed claim

[NSchatz]

Replaces the blanket "fails closed" property in the README and docs-content with the cases the library states it blocks. The per-format fail-closed rows and rules (HL7, C-CDA, FHIR, X12, free text) are unchanged. Checked on the published @cosyte/deid 0.1.0 from a clean install outside any repository: on a synthetic HL7 v2 message, OBX-5 and NTE free text and a Z-segment are blocked (DEID_FREETEXT_BLOCKED, DEID_LOCUS_BLOCKED) and none of their text reaches the output.

File	Before	After
README.md (tagline)	a HIPAA-grounded policy engine that fails closed and emits a value-free manifest	a HIPAA-grounded policy engine that emits a value-free manifest
README.md	a de-identifier is conservative and fails closed.	a de-identifier is conservative.
README.md (design)	Fail-closed rule: anything uncertain is blocked, never passed through	Fail-closed rule: an unrecognized structure, an un-locatable identifier or free text is blocked, never passed through
docs-content/intro.md	a de-identifier is conservative; it fails closed. An unrecognized structure or an un-locatable identifier is blocked	a de-identifier is conservative: an unrecognized structure or an un-locatable identifier is blocked
docs-content/quickstart.md	@cosyte/deid fails closed: anything it cannot confidently handle is blocked	In @cosyte/deid, an unrecognized structure or an un-locatable identifier is blocked
docs-content/limitations.md	The library fails closed: on any ambiguity it blocks or removes	On an unrecognized structure, an un-locatable identifier, an unknown segment or extension, or a free-text blob, the library blocks or removes
docs-content/limitations.md	structured-field, fail-closed, policy-driven Safe-Harbor transformation with a value-free manifest, never a leaked patient, never a destroyed clinical value, and never a claim of "de-identified."	structured-field, policy-driven Safe-Harbor transformation with a value-free manifest, never a leaked patient, and never a claim of "de-identified."
docs-content/concepts-archetype.md	on any ambiguity (an unrecognized structure, ...)	on each of these ambiguities (an unrecognized structure, ...)
examples/fail-closed.ts (docblock)	anything it cannot confidently handle is blocked or refused	each case below is blocked or refused

No runnable block and none of the sentences deidentify-fhir.test.ts reads from limitations.md change. prettier --check passes on README.md and the example. The package.json description changes only with a release.

https://claude.ai/code/session_011dC8vE9axM3hqC8rNEX3W9